Vitamin B12

Uses

Vitamin B12 is a water-soluble vitamin needed for normal nerve cell activity, DNA replication, and production of the mood-affecting substance SAMe (S-adenosyl-L-methionine). Vitamin B12 acts with folic acid and vitamin B6 to control homocysteine levels. An excess of homocysteine is associated with an increased risk of heart disease, stroke, and potentially other diseases such as osteoporosis and Alzheimer’s disease.

What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used for Why
3 Stars
Anemia and Vitamin B12 Deficiency
600 to 1,000 mcg daily
Taking vitamin B12 may help prevent and treat anemia. Deficiencies of iron, vitamin B12, and folic acid are the most common nutritional causes of anemia.

Deficiencies of iron, , and folic acid are the most common nutritional causes of anemia. Although rare, severe deficiencies of several other vitamins and minerals, including vitamin A,vitamin B2,vitamin B6,vitamin C, and copper, can also cause anemia by various mechanisms. Rare genetic disorders can cause anemias that may improve with large amounts of supplements such as vitamin B1.
3 Stars
Depression and Vitamin B12 Deficiency
See a doctor for evaluation
Taking vitamin B12 can help counteract deficiencies related to depression.

Deficiency of can create disturbances in mood that respond to B12 supplementation. Significant vitamin B12 deficiency is associated with a doubled risk of severe depression, according to a study of physically disabled older women. Depression caused by vitamin B12 deficiency can occur even if there is no B12 deficiency-related anemia.

Mood has been reported to sometimes improve with high amounts of vitamin B12 (given by injection), even in the absence of a B12 deficiency. Supplying the body with high amounts of vitamin B12 can only be done by injection. However, in the case of overcoming a diagnosed B12 deficiency, one can follow an initial injection with oral maintenance supplementation (1 mg per day), even when the cause of the deficiency is a malabsorption problem such as pernicious anemia.
3 Stars
High Homocysteine (Vitamin B6, Folic Acid)
400 to 1,000 mcg of folic acid daily, 10 to 50 mg of vitamin B6 daily, and 50 to 300 mcg of vitamin B12 daily
Vitamin B6, folic acid, and vitamin B12 all play a role in converting homocysteine to other substances within the body and have consistently lowered homocysteine levels in trials.

Vitamin B6 , folic acid, and all play a role in converting homocysteine to other substances within the body. By so doing, they consistently lower homocysteine levels in research trials, a finding that is now well accepted. Several studies have used (and some doctors recommend) 400–1,000 mcg of folic acid per day, 10–50 mg of vitamin B6 per day, and 50–300 mcg of vitamin B12 per day.

Of these three vitamins, folic acid supplementation lowers homocysteine levels the most for the average person. It also effectively lowers homocysteine in people on kidney dialysis. In 1996, the FDA required that all enriched flour, rice, pasta, cornmeal, and other grain products contain 140 mcg of folic acid per 3½ ounces. This level of fortification has led to a measurable decrease in homocysteine levels. However, even higher levels of food fortification with folic acid have been reported to be more effective in lowering homocysteine, suggesting that the FDA-mandated supplementation is inadequate to optimally protect people against high homocysteine levels. Therefore, people wishing to lower their homocysteine levels should continue to take folic acid supplements despite the FDA-mandated fortification program.
3 Stars
Neuropathy (Vitamin B6, Folic Acid)
2,000 mcg methylcobalamin (B12); 3,000 mcg methylfolate (B9); and 35 mg pyridoxal 5-phosphate once to twice daily
B vitamins, and vitamin B12 in particular, may be helpful in treating various types of neuropathies. People with type 2 diabetes taking metformin should be monitored for B12 deficiency.
Vitamin B12 has demonstrated neuroprotective and analgesic effects and has been found to have benefits in treating peripheral neuropathy from various causes. Vitamin B12 deficiency is common in people with type 2 diabetes, and a widely used anti-diabetes medication, metformin, has been found to induce vitamin B12 deficiency. Vitamin B12 deficiency has been associated in some, but not all, studies with increased risk of diabetic neuropathy. A possible link between low folate levels and diabetic neuropathy has also been reported. Preliminary trials using combinations of active forms of oral vitamin B12, folate, and vitamin B6 found they have a positive effect on diabetic neuropathy symptoms and quality of life. In a comparison trial, vitamin B12 injections were found to be more effective than the pain medication, nortriptyline, for reducing diabetic neuropathy symptoms. One meta-analysis of 17 clinical trials found the combination of intramuscular or intravenous vitamin B12 plus intravenous alpha-lipoic acid may be more effective than vitamin B12 alone. The possible role of vitamin B12 and other B vitamins in preventing or treating chemotherapy-induced neuropathy is suggested by laboratory and animal research, but findings from human trials have not been conclusive.
3 Stars
Type 1 Diabetes
1,500 micrograms daily
Supplementing with vitamin B12 may improve symptoms of diabetic neuropathy.
Vitamin B12, or cobalamin, is needed for normal functioning of nerve cells and is also involved in homocysteine metabolism. People with type 1 diabetes have an increased risk of other disorders that can affect their B12 status, such as autoimmune gastritis, celiac disease, and pernicious anemia. Vitamin B12, taken at a dose of 1,500 micrograms per day for 24 weeks, has been found to reduce symptoms and disability due to diabetic nerve damage (neuropathy). In a preliminary trial that included 544 participants with diabetic neuropathy, supplementing with vitamin B12 (in the form of methylcobalamin) along with folic acid (in the form of methylfolate) and vitamin B6 (in the form of pyridoxal-5-phosphate) for 12 weeks was associated with a 35% drop in symptom scores and a 32% drop in pain scores. A comparison trial in 100 subjects with diabetic neuropathy found injections of B12 were more effective than the commonly used pain medication, nortriptyline, for treating symptoms of diabetic neuropathy. A number of other studies have shown B12, alone and in combination with other treatments such as alpha-lipoic acid and prostaglandin E1, can be beneficial in those with diabetic neuropathy. Oral vitamin B12 up to 1,500 micrograms per day is recommended by some practitioners.
2 Stars
Age-Related Cognitive Decline (Folic Acid)
100 mcg per day of vitamin B12 and 400 mcg per day of folic acid
In a double-blind trial, supplementing with vitamin B12 and folic acid for 2 years slowed the rate of cognitive decline, compared with placebo, in elderly volunteers.
In a double-blind trial, supplementation with 100 mcg per day of vitamin B12 and 400 mcg per day of folic acid for 2 years slowed the rate of cognitive decline, compared with placebo, in elderly volunteers.
2 Stars
Age-Related Cognitive Decline (Vitamin B6, Folic Acid)
Refer to label instructions
In women with cardiovascular disease or related risk factors and low dietary intake of folic acid, vitamin B6, and vitamin B12, supplementing with a combination of these nutrients may protect against age-related cognitive decline.

In a study of female health professionals who had cardiovascular disease or cardiovascular disease risk factors, daily supplementation with folic acid (2.5 mg), vitamin B6 (50 mg), and vitamin B12 (1 mg) for 5.4 years had no effect on cognitive function. However, supplementation appeared to prevent age-related cognitive decline in the 30% of women who had low dietary intake of B vitamins.

Supplementation with homocysteine-lowering B vitamins (folic acid, vitamin B12, and vitamin B6) also slowed the rate of brain atrophy in elderly people who had mild cognitive impairment and high homocysteine levels.
2 Stars
Age-Related Cognitive Decline and Vitamin B12 Deficiency
Consult a qualified healthcare practitioner
Improved brain function among seniors has been observed after correcting vitamin B12 deficiency with injections, but oral vitamin B12 has not been studied for ARCD. People with ARCD should be tested for vitamin B12 deficiency.

Supplementation with may improve cognitive function in elderly people who have been diagnosed with a B12 deficiency. Such a deficiency in older people is not uncommon. In a preliminary trial, intramuscular injections of 1,000 mcg of vitamin B12 were given once per day for a week, then weekly for a month, then monthly thereafter for 6 to 12 months. Researchers noted “striking” improvements in cognitive function among 22 elderly people with vitamin B12 deficiency and cognitive decline. Cognitive disorders due to vitamin B12 deficiency may also occur in people who do not exhibit the anemia that often accompanies vitamin B12 deficiency. For example, in a study of 141 elderly people with cognitive abnormalities due to B12 deficiency, 28% had no anemia. All participants were given intramuscular injections of vitamin B12, and all showed subsequent improvement in cognitive function.

Vitamin B12 injections put more B12 into the body than is achievable with absorption from oral supplementation. Therefore, it is unclear whether the improvements in cognitive function described above were due simply to correcting the B12 deficiency or to a therapeutic effect of the higher levels of vitamin B12 obtained through injection. Elderly people with ARCD should be evaluated by a healthcare professional to see if they have a B12 deficiency. If a deficiency is present, the best way to proceed would be initially to receive vitamin B12 injections. If the injections result in cognitive improvement, some doctors would then recommend an experimental trial with high amounts of oral B12, despite a current lack of scientific evidence. If oral vitamin B12 is found to be less effective than B12 shots, the appropriate treatment would be to revert to injectable B12. At present, no research trials support the use of any vitamin B12 supplementation in people who suffer from ARCD but are not specifically deficient in vitamin B12.
2 Stars
Bell’s Palsy
Consult a qualified healthcare practitioner
Vitamin B12 injections have been shown to be beneficial for people with Bell’s palsy.

deficiency can cause nerve degeneration, and both oral and injected vitamin B12 have been used to treat many types of nerve disorders. One older case report described successful treatment of chronic Bell’s palsy with vitamin B12 injections of 500 to 1,000 mcg given every one to two days. A more recent trial compared the effect of 500 mcg of injected vitamin B12 (in the form of methylcobalamin) given three times weekly for at least eight weeks—steroid medication, or both. Researchers found significantly faster recovery in the groups given B12 injections with or without steroids, compared to those given steroids alone. These findings agree with earlier reports on the effectiveness of methylcobalamin injections for Bell’s palsy. It is unlikely that oral vitamin B12 would be similarly effective. People seeking B12 injections should consult a physician.
2 Stars
Celiac Disease (Vitamin B6, Folic Acid)
3 mg vitamin B6, 0.8 mg folic acid, and 0.5 mg vitamin B12
Daily supplementation with a combination of vitamin B6 (3 mg), folic acid (0.8 mg), and vitamin B12 (0.5 mg) have been shown to help relieve depression in people with celiac disease.
In one trial, 11 people with celiac disease suffered from persistent depression despite being on a gluten-free diet for more than two years. However, after supplementation with vitamin B6 (80 mg per day) for six months, the depression disappeared. Daily supplementation with a combination of vitamin B6 (3 mg), folic acid (0.8 mg), and vitamin B12 (0.5 mg) for 6 months also improved psychological well-being in people with long-standing celiac disease who had poor psychological well-being despite being on a strict gluten-free diet.
2 Stars
Chronic Fatigue Syndrome
Consult a qualified healthcare practitioner
Vitamin B12 deficiency may cause fatigue, but B12 injections have been reported benefits even without deficiency. A doctor should evaluate deficiency and whether B12 injections may help.

deficiency may cause fatigue. However, some reports, even double-blind ones, have shown that people who are not deficient in B12 have increased energy following a series of vitamin B12 injections. Some sources in conventional medicine have discouraged such people from taking B12 shots despite this evidence. Nonetheless, some doctors have continued to take the limited scientific support for B12 seriously. In one preliminary trial, 2,500 to 5,000 mcg of vitamin B12 given by injection every two to three days led to improvement in 50 to 80% of a group of people with CFS; most improvement appeared after several weeks of B12 shots. While the research in this area remains preliminary, people with CFS considering a trial of vitamin B12 injections should consult a doctor. Oral or sublingual B12 supplements are unlikely to obtain the same results as injectable B12, because the body’s ability to absorb large amounts is relatively poor.
2 Stars
Hepatitis and Hepatitis C
Refer to label instructions
In one study, the addition of vitamin B12 injections to antiviral medications increased the proportion of patients in whom the hepatitis C virus was cleared from the body.
(with or without folic acid) has been reported in trials from the 1950s to help some people with hepatitis. In a more recent study, the addition of vitamin B12 injections (5,000 mcg every 4 weeks) to antiviral medications increased the proportion of patients in whom the hepatitis C virus was cleared from the body. Vitamin B12 injections are likely to be more beneficial than oral administration.
2 Stars
Indigestion and Vitamin B12 Deficiency, Delayed Gastric Emptying, and Helicobacter Pylori Infection
1,000 mcg daily
Vitamin B12 may be beneficial for people with delayed emptying of the stomach in association with Helicobacter pylori infection and low blood levels of vitamin B12.

supplementation may be beneficial for a subset of people suffering from indigestion: those with delayed emptying of the stomach contents in association with Helicobacter pylori infection and low blood levels of vitamin B12. In a double-blind study of people who satisfied those criteria, treatment with vitamin B12 significantly reduced symptoms of dyspepsia and improved stomach-emptying times.
2 Stars
Low Back Pain (Vitamin B1, Vitamin B6)
Take under medical supervision: 50 to 100 mg each of vitamins B1 and B6, and 250 to 500 mcg of vitamin B12, all taken three times per day
A combination of vitamin B1, vitamin B6, and vitamin B12 may prevent a common type of back pain linked to vertebral syndromes and may reduce the need for anti-inflammatory medications.

A combination of vitamin B1, vitamin B6, and has proved useful for preventing a relapse of a common type of back pain linked to vertebral syndromes, as well as reducing the amount of anti-inflammatory medications needed to control back pain, according to double-blind trials. Typical amounts used have been 50–100 mg each of vitamins B1 and B6, and 250–500 mcg of vitamin B12, all taken three times per day. Such high amounts of vitamin B6 require supervision by a doctor.
2 Stars
Macular Degeneration (Vitamin B6, Folic Acid)
2.5 mg folic acid, 50 mg vitamin B6, and 1 mg vitamin B12
In a double-blind study of female health professionals who had cardiovascular disease or risk factors, daily supplementation with folic acid, vitamin B6, and vitamin B12 significantly decreased age-related macular degeneration.

In a double-blind study of female health professionals who had cardiovascular disease or cardiovascular disease risk factors, daily supplementation with folic acid (2.5 mg), vitamin B6 (50 mg), and vitamin B12 (1 mg) for 7.3 years significantly decreased the incidence of age-related macular degeneration. 

2 Stars
Male Infertility
1,500 mcg daily
Vitamin B12 is needed to maintain fertility. Vitamin B12 injections have been shown to increase sperm counts. Men

is needed to maintain fertility. Vitamin B12 injections have increased sperm counts for men with low numbers of sperm. These results have been duplicated in double-blind research. In one study, a group of infertile men were given oral vitamin B12 supplements (1,500 mcg per day of methylcobalamin) for 2 to 13 months. Approximately 60% of those taking the supplement experienced improved sperm counts. However, controlled trials are needed to confirm these preliminary results. Men seeking vitamin B12 injections should consult a physician.
2 Stars
Migraine Headache
1 mg daily
In a preliminary trial, vitamin B12 reduced the frequency of migraine attacks by at least 50% in 10 of 19 people with recurrent migraines.

In a preliminary trial, administration of 1 mg of per day (by the intranasal route) for 3 months reduced the frequency of migraine attacks by at least 50% in 10 of 19 people with recurrent migraines. A placebo-controlled study is needed to determine how much of this improvement was due to a placebo effect.
2 Stars
Osteoporosis and High Homocysteine
1,500 mcg with 5 mg of folic acid daily
Homocystinuria, a condition associated with high homocysteine levels, frequently causes osteoporosis. By lowering homocysteine levels, vitamin B12 may help prevent osteoporosis.
Folic acid , vitamin B6, and are known to reduce blood levels of the amino acid homocysteine, and homocystinuria, a condition associated with high homocysteine levels, frequently causes osteoporosis. Therefore, some researchers have suggested that these vitamins might help prevent osteoporosis by lowering homocysteine levels. In a double-blind study of people who had suffered a stroke and had high homocysteine levels, daily supplementation with 5 mg of folic acid and 1,500 mcg of vitamin B12 for two years reduced the incidence of fractures by 78%, compared with a placebo. The reduction in fracture risk appeared to be due to an improvement in bone quality, rather than to a change in bone mineral density. However, supplementation with these vitamins did not reduce fracture risk in people who had only mildly elevated homocysteine levels and relatively high pretreatment folic acid levels. For the purpose of lowering homocysteine, amounts of folic acid and vitamins B6 and B12 found in high-potency B-complex supplements and multivitamins should be adequate.
2 Stars
Schizophrenia and High Homocysteine (Vitamin B6, Folic Acid)
Take folic acid (2 mg), vitamin B6 (25 mg), and vitamin B12 (400 mcg) daily
People with schizophrenia who have high homocysteine levels may improve symptoms by supplementing with folic acid, vitamin B6, and vitamin B12.
In another double-blind study, daily supplementation with folic acid (2 mg), vitamin B6 (25 mg), and (400 mcg) for three months improved symptoms of schizophrenia compared with a placebo. All of the participants in this study had elevated blood levels of homocysteine, which can be decreased by taking these three B vitamins. Based on this study, it would seem reasonable to measure homocysteine levels in people with schizophrenia and, if they are elevated, to supplement with folic acid, vitamin B6, and vitamin B12.
2 Stars
Sickle Cell Anemia and Vitamin B12 Deficiency
Consult a qualified healthcare practitioner
People with sickle cell anemia may be deficient in vitamin B12. Intramuscular vitamin B12 injections improved symptoms for patients in one study.

Sickle cell anemia may result in deficiency. A study of children with sickle cell anemia found them to have a higher incidence of vitamin B12 deficiency than children without the disease. A study of 85 adults with sickle cell anemia showed more of them had vitamin B12 deficiency than did a group of healthy people. A subsequent preliminary trial demonstrated that for patients with low blood levels of vitamin B12, intramuscular injections of 1 mg of vitamin B12 weekly for 12 weeks led to a significant reduction in symptoms. Researchers do not know whether people with sickle cell anemia who are found to be deficient in vitamin B12 would benefit equally from taking vitamin B12 supplements orally.

Preliminary research has found that patients with sickle cell anemia are more likely to have elevated blood levels of homocysteine compared to healthy people. Elevated homocysteine is recognized as a risk factor for cardiovascular disease. In particular, high levels of homocysteine in sickle cell anemia patients have been associated with a higher incidence of stroke. Deficiencies of vitamin B6, vitamin B12, and folic acid occur more frequently in people with sickle cell anemia than in others and are a cause of high homocysteine levels. A controlled trial found homocysteine levels were reduced 53% in children with sickle cell anemia receiving a 2–4 mg supplement of folic acid per day, depending on age, but vitamin B6 or B12 had no effect on homocysteine levels. A double-blind trial of children with sickle cell anemia found that children given 5 mg of folic acid per day had less painful swelling of the hands and feet compared with those receiving placebo, but blood abnormalities and impaired growth rate associated with sickle cell anemia were not improved. In the treatment of sickle cell anemia, folic acid is typically supplemented in amounts of 1,000 mcg daily. Anyone taking this amount of folic acid should have vitamin B12 status assessed by a healthcare professional.
2 Stars
Thalassemia and Vitamin B12 Deficiency
If deficient: 300 to1,000 mcg daily
Some studies have found people with thalassemia to be frequently deficient in vitamin B12, supplementing with the vitamin may help.

Test tube studies have shown that propionyl-L-carnitine (a form of L-carnitine) protects red blood cells of people with thalassemia against free radical damage. In a preliminary study, children with beta thalassemia major who took 100 mg of L-carnitine per 2.2 pounds of body weight per day for three months had a significantly decreased need for blood transfusions. Some studies have found people with thalassemia to be frequently deficient in folic acid, , and zinc. Researchers have reported improved growth rates in zinc-deficient thalassemic children who were given zinc supplements of 22.5 to 90 mg per day, depending on age.Magnesium has been reported to be low in thalassemia patients in some, but not all, studies. A small, preliminary study reported that oral supplements of magnesium, 7.2 mg per 2.2 pounds of body weight per day, improved some red blood cell abnormalities in thalassemia patients.
2 Stars
Type 2 Diabetes and Diabetic Neuropathy (Vitamin B1)
Refer to label instructions
Taking vitamin B1 combined with vitamin B12 may improve symptoms of diabetic neuropathy.
A controlled trial in Africa found that supplementing with both vitamin B1 (25 mg per day) and vitamin B6 (50 mg per day) led to significant improvement of symptoms of diabetic neuropathy after four weeks. However, since this was a trial conducted among people in a vitamin B1–deficient developing country, these improvements might not occur in other people with diabetes. Another trial found that combining vitamin B1 (in a special fat-soluble form) and vitamin B6 plus in high but variable amounts led to improvement in some aspects of diabetic neuropathy in 12 weeks. As a result, some doctors recommend that people with diabetic neuropathy supplement with vitamin B1, though the optimal level of intake remains unknown.
2 Stars
Type 2 Diabetes and Diabetic Neuropathy
1 to 10 mg daily
Vitamin B12 deficiency is common in people being treated medically for type 2 diabetes. Supplementation can restore healthy levels and prevent dangerous long-term consequences of B12 deficiency.
Multiple studies have reported finding an association between long-term metformin use in people with type 2 diabetes and vitamin B12 deficiency. Although this metformin-associated B12 deficiency does not appear to be linked to diabetic neuropathy (nerve dysfunction), it is nonetheless important to restore normal B12 status to avoid complications of B12 deficiency such as anemia, immune dysfunction, and neurological disorders.
2 Stars
Urinary Incontinence (if deficient )
See a doctor to test for deficiency
Vitamin B12 deficency can cause urinary incontinence that may be corrected with supplementation.
Vitamin B12 deficency can cause urinary incontinence that can be cured with B12 supplementation. One preliminary study, but not others, have found that low blood levels of B12 were associated with urinary incontinence in older people. Controlled trials are needed to determine whether B12 supplementation might be useful as a treatment for the common types of urinary incontinence.
2 Stars
Vitiligo
Refer to label instructions
Studies have shown vitamin B12 to be effective at skin repigmentation in people with vitiligo.

A clinical report describes the use of vitamin supplements in the treatment of vitiligo.Folic acid and/or and vitamin C levels were abnormally low in most of the 15 people studied. Supplementation with large amounts of folic acid (1–10 mg per day), along with vitamin C (1 gram per day) and intramuscular vitamin B12 injections (1,000 mcg every two weeks), produced marked repigmentation in eight people. These improvements became apparent after three months, but complete repigmentation required one to two years of continuous supplementation. In another study of people with vitiligo, oral supplementation with folic acid (10 mg per day) and vitamin B12 (2,000 mcg per day), combined with sun exposure, resulted in some repigmentation after three to six months in about half of the participants. This combined regimen was more effective than either vitamin supplementation or sun exposure alone.
1 Star
Alzheimer’s Disease
Refer to label instructions
Some researchers feel Alzheimer’s disease may be related to vitamin B12 deficiency.

Some researchers have found an association between Alzheimer’s disease and deficiencies of and folic acid; however, other researchers consider such deficiencies to be of only minor importance. In a study of elderly Canadians, those with low blood levels of folate were more likely to have dementia of all types, including Alzheimer’s disease, than those with higher levels of folate. Little is known about whether supplementation with either vitamin would significantly help people with this disease. Nonetheless, it makes sense for people with Alzheimer’s disease to be medically tested for vitamin B12 and folate deficiencies and to be treated if they are deficient.

1 Star
Asthma
Refer to label instructions
In some people, asthma symptoms can be triggered by ingesting sulfites, a food additive. Pretreatment with a large amount of vitamin B12 reduced some children’s asthmatic reaction to sulfites in one trial.

In some people with asthma, symptoms can be triggered by ingestion of food additives known as sulfites. Pretreatment with a large amount of (1,500 mcg orally) reduced the asthmatic reaction to sulfites in children with sulfite sensitivity in one preliminary trial. The trace mineral molybdenum also helps the body detoxify sulfites. While some doctors use molybdenum to treat selected patients with asthma, there is little published research on this treatment, and it is not known what an appropriate level of molybdenum supplementation would be. A typical American diet contains about 200 to 500 mcg per day, and preliminary short-term trials have used supplemental amounts of 500 mcg per day. People who suspect sulfite-sensitive asthma should consult with a physician before taking molybdenum.
1 Star
Atherosclerosis
Refer to label instructions
Blood levels of the amino acid homocysteine have been linked to atherosclerosis and heart disease in most research. Taking vitamin B12 may help lower homocysteine levels.

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research, though uncertainty remains about whether elevated homocysteine actually causes heart disease. Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes, evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, , and folic acid are associated with low levels of homocysteine and supplementing with these vitamins lowers homocysteine levels.

While several trials have consistently shown that B6, B12, and folic acid lower homocysteine, the amounts used vary from study to study. Many doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid. Even researchers finding only inconsistent links between homocysteine and heart disease have acknowledged that a B vitamin might offer protection against heart disease independent of the homocysteine-lowering effect. In one trial, people with normal homocysteine levels had demonstrable reversal of atherosclerosis when supplementing B vitamins (2.5 mg folic acid, 25 mg vitamin B6, and 250 mcg of vitamin B12 per day). Similar results were seen in another study.

For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective. Of these four supplements, folic acid appears to be the most important. Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful.
1 Star
Bipolar Disorder
Refer to label instructions
Vitamin B12 deficiency has been associated with both mania and depression. In one study, these symptoms cleared after treatment with B12 injections.

Both folic acid and are used in the body to manufacture serotonin and other neurotransmitters. It is well known that deficiency of either nutrient is associated with depression. There is some evidence that patients diagnosed with mania are also more likely to have folate deficiencies than healthy controls. Other studies, however, have found that folic acid deficiency was not more common in bipolar patients taking lithium than in healthy people. Some studies have found that people who take lithium long term, and who also have high blood levels of folic acid, respond better to lithium. Not all studies have confirmed these findings, however. A double-blind study of patients receiving lithium therapy showed that the addition of 200 mcg of folic acid per day resulted in clinical improvement, whereas placebo did not.

There have been case reports of both mania and depression associated with vitamin B12 deficiency, and these symptoms cleared after treatment with injections of B12. However, B12 deficiency has not been reported in bipolar disorder patients, and no studies have been published investigating the effects of vitamin B12 supplementation in people with bipolar disorder.
1 Star
Bursitis
Refer to label instructions
Vitamin B12 injections have been shown to relieve symptoms of acute shoulder bursitis and decrease the amount of calcification in some cases.

In a preliminary study, intramuscular injections of relieved the symptoms of acute subdeltoid (shoulder) bursitis and also decreased the amount of calcification in some cases. This mechanism is not understood. Oral B vitamins are unlikely to have the same effect, since the body’s absorption of vitamin B12 is quite limited. A doctor should be consulted regarding B12 or B12 injections.
1 Star
Canker Sores
3 to 1,000 mcg daily
Recurrent canker sores might be related to vitamin B12 deficiency, but research has shown that even without deficiency supplementing this vitamin may be beneficial.

Several preliminary studies, though not all, have found a surprisingly high incidence of iron and B vitamin deficiency among people with recurrent canker sores. Treating these deficiencies has been reported in preliminary and controlled studies to reduce or eliminate recurrences in most cases. In addition, a double-blind study found that supplementing with vitamin B12 prevented recurrences even in people who were not deficient in the vitamin. The amount used in that study was 1,000 mcg twice a day for six months. Supplementing daily with B vitamins—300 mg vitamin B1, 20 mg vitamin B2, and 150 mg vitamin B6—has been reported to provide some people with relief. Thiamine (B1) deficiency specifically has been linked to an increased risk of canker sores. The right supplemental level of iron requires diagnosis of an iron deficiency by a healthcare professional using lab tests.

1 Star
Crohn’s Disease
Refer to label instructions
Vitamin B12 is needed to repair intestinal cells damaged by Crohn’s disease. Supplementation may offset some of the deficiency caused by Crohn’s-related malabsorption.

Crohn’s disease often leads to malabsorption. As a result, deficiencies of many nutrients are common. For this reason, it makes sense for people with Crohn’s disease to take a high potency multivitamin-mineral supplement. In particular, deficiencies in zinc, folic acid, , vitamin D, and iron have been reported. Zinc, folic acid, and vitamin B12 are all needed to repair intestinal cells damaged by Crohn’s disease. Some doctors recommend 25 to 50 mg of zinc (balanced with 2 to 4 mg of copper), 800 mcg of folic acid, and 800 mcg of vitamin B12. Iron status should be evaluated by a doctor before considering supplementation.
1 Star
Dermatitis Herpetiformis and Vitamin B12 Deficiency
Refer to label instructions
Supplementing with vitamin B12 can counteract the nutrient deficiency that often occurs as a result of malabsorption.

People with DH frequently have mild malabsorption (difficulty absorbing certain nutrients) associated with low stomach acid (hypochlorhydria) and inflammation of the stomach lining (atrophic gastritis). Mild malabsorption may result in anemia and nutritional deficiencies of iron, folic acid,, and zinc. More severe malabsorption may result in loss of bone mass. Additional subtle deficiencies of vitamins and minerals are possible, but have not been investigated. Therefore, some doctors recommend people with DH have their nutritional status checked regularly with laboratory studies. These doctors may also recommend multivitamin-mineral supplements and, to correct the low stomach acid, supplemental betaine HCl (a source of hydrochloric acid).
1 Star
Down Syndrome
Refer to label instructions
People with Down syndrome may be deficient in vitamin B12 and may benefit from supplementation.

The red blood cells of people with Down syndrome are unusual in ways that suggest either or folic acid deficiency. However, folic acid levels have been found to be normal in each of these studies, and only one study has found lower levels of vitamin B12 in Down syndrome as compared with healthy individuals. Intervention trials using either vitamin B12 or folic acid have not been done.
1 Star
Heart Attack
Refer to label instructions
Taking vitamin B12 may reduce blood levels of homocysteine. High homocysteine levels have been linked to an increased heart attack risk.

High blood levels of the amino acid homocysteine have been linked to an increased risk of heart attack in most, though not all, studies. A blood test screening for levels of homocysteine, followed by supplementation with 400 mcg of folic acid and 500 mcg of vitamin B12 per day could prevent a significant number of heart attacks, according to one analysis.Folic acid and vitamins B6 and are known to lower homocysteine.

There is a clear association between low blood levels of folate and increased risk of heart attacks in men. Based on the available research, some doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid per day for people at high risk of heart attack.

1 Star
HIV and AIDS Support
Refer to label instructions
In HIV-positive people with B-vitamin deficiency, B vitamins appear to delay progression to and death from AIDS.

In HIV-positive people with B-vitamin deficiency, the use of B-complex vitamin supplements appears to delay progression to and death from AIDS. Thiamine (vitamin B1) deficiency has been identified in nearly one-quarter of people with AIDS. It has been suggested that a thiamine deficiency may contribute to some of the neurological abnormalities that are associated with AIDS. Vitamin B6 deficiency was found in more than one-third of HIV-positive men; vitamin B6 deficiency was associated with decreased immune function in this group. In a population study of HIV-positive people, intake of vitamin B6 at more than twice the recommended dietary allowance (RDA is 2 mg per day for men and 1.6 mg per day for women) was associated with improved survival. Low blood levels of folic acid and are also common in HIV-positive people.
1 Star
Hives
Refer to label instructions
Vitamin B12 injections have been reported to reduce the severity of acute hives and the frequency and severity of outbreaks in chronic cases.

has been reported to reduce the severity of acute hives as well as to reduce the frequency and severity of outbreaks in chronic cases. The amount used in these reported case studies was 1,000 mcg by injection per week. Whether taking B12 supplements orally would have these effects remains unknown. On rare occasions, vitamin B12 injections cause hives in susceptible people. Whether such reactions are actually triggered by exposure to large amounts of vitamin B12 or to preservatives and other substances found in most vitamin B12 injections remains unclear.
1 Star
Immune Function
Refer to label instructions
A deficiency of vitamin B12 has been associated with decreased immune function. Restoring vitamin B12 levels may improve levels of immune cells.
A deficiency of has been associated with decreased immune function. In a controlled trial, people with vitamin B12 deficiency anemia were also found to have markedly decreased levels of white blood cells associated with immune function. Restoration of vitamin B12 stores by means of injections improved levels of these immune cells, suggesting an important role for vitamin B12 in immune function.
1 Star
Insomnia
Refer to label instructions
In two small preliminary trials, people with insomnia resulting from disorders of the sleep-wake rhythm improved after supplementing with vitamin B12.

In two small preliminary trials, people with insomnia resulting from disorders of the sleep-wake rhythm improved after supplementing with (1,500 to 3,000 mcg per day).
1 Star
Lung Cancer
Refer to label instructions
Together, folic acid and vitamin B12 help cells replicate normally. In one trial, smokers with precancerous lung changes who were given folic acid and vitamin B12 saw a significant reversal of their condition.
Folic acid and work together in the body to help cells replicate normally. In a double-blind trial, smokers with precancerous changes in the lungs were given a placebo or the combination of 10,000 mcg of folic acid and 500 mcg of vitamin B12 per day for four months. A significant reversal of precancerous changes occurred in those given vitamin supplements compared with those given the placebo.
1 Star
Pain
Refer to label instructions
Vitamin B12 appears to have pain-killing properties. In people with vertebral pain syndromes, injections of massive amounts of vitamin B12 have reportedly relieved pain.

has exhibited pain-killing properties in animal studies. In humans with vertebral pain syndromes, injections of massive amounts of vitamin B12 (5,000 to 10,000 mcg per day) have reportedly provided pain relief. Further studies are needed to confirm the efficacy of this treatment.
1 Star
Phenylketonuria and Vitamin B12 Deficiency
Refer to label instructions
Vitamin B12 is found almost exclusively in foods of animal origin, which are restricted on the PKU diet. Supplementing with vitamin B12 may correct a deficiency.

People with PKU may be deficient in several nutrients, due to the restricted diet which is low in protein and animal fat. Deficiencies of long-chain polyunsaturated fatty acids (LC-PUFAs),selenium,, and vitamin K may develop on this diet.

is found almost exclusively in foods of animal origin, which are restricted on the PKU diet. People on the PKU diet who are inconsistent in their use of a vitamin B12 supplement may become deficient in this vitamin. In a survey of young adults with PKU, 32% were found to have low or low-normal blood levels of vitamin B12.Vitamin B12 deficiency can cause anemia and nerve problems.

1 Star
Pre- and Post-Surgery Health
Refer to label instructions
In one trial, a combination of vitamins B1, B6, and B12 before and after surgery prevented post-surgical reductions in immune activity.

Vitamin B1 , given as intramuscular injections of 120 mg daily for several days before surgery, resulted in less reduction of immune system activity after surgery in a preliminary trial. In a controlled trial, an oral B vitamin combination providing 100 mg of B1, 200 mg of vitamin B6, and 200 mcg of daily given for five weeks before surgery and for two weeks following surgery also prevented post-surgical reductions in immune activity. However, no research has explored any other benefits of B vitamin supplementation in surgery patients.
1 Star
Retinopathy
Refer to label instructions
In one study, adding vitamin B12 to the insulin injections of children with diabetic retinopathy helped relieve symptoms.

One study investigated the effect of adding 100 mcg per day of to the insulin injections of 15 children with diabetic retinopathy. After one year, signs of retinopathy disappeared in 7 of 15 cases; after two years, 8 of 15 were free of retinopathy. Adults with diabetic retinopathy did not benefit from vitamin B12 injections. Consultation with a physician is necessary before adding injectable vitamin B12 to insulin.
1 Star
Schizophrenia
Refer to label instructions
People with schizophrenia may have low vitamin B12 levels. Supplementing with the vitamin may correct an imbalance and improve symptoms.

deficiency can cause symptoms that are similar to those of schizophrenia and one case has been reported in which such symptoms cleared after supplementation with vitamin B12. Some studies have reported finding lower levels of vitamin B12 in people with schizophrenia than in the general population, but others have found no difference. No trials of vitamin B12 supplementation in schizophrenic patients have been published.
1 Star
Seborrheic Dermatitis in Adults
Refer to label instructions
Vitamin B12 injections have been reported to improve adult seborrheic dermatitis.

One physician reported that injections of B-complex vitamins were useful in the treatment of seborrheic dermatitis in infants. A preliminary trial found that 10 mg per day of folic acid was helpful in 17 of 20 cases of adult seborrheic dermatitis. However, this study also found that oral folic acid did not benefit infants with cradle cap. A preliminary study found that topical application of vitamin B6 ointment (containing 10 mg B6 per gram of ointment) to affected areas improved adult seborrheic dermatitis. However, oral vitamin B6 (up to 300 mg per day) was ineffective. Injections of were reported to improve in 86% of adults with seborrheic dermatitis in a preliminary trial. Oral administration of vitamin B12 for seborrheic dermatitis has not been studied.
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Shingles and Postherpetic Neuralgia
Refer to label instructions
Vitamin B12 injections may relieve the symptoms of postherpetic neuralgia.

Some doctors have observed that injections of appear to relieve the symptoms of postherpetic neuralgia. However, since these studies did not include a control group, the possibility of a placebo effect cannot be ruled out. Oral vitamin B12 supplements have not been tested, but they are not likely to be effective against postherpetic neuralgia.
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Stroke and High Homocysteine
Refer to label instructions
Elevated blood levels of homocysteine have been linked to stroke risk in most studies. Supplementing with vitamin B12 may lower homocysteine levels and reduce stroke risk.

Elevated blood levels of homocysteine, a toxic amino acid byproduct, have been linked to risk of stroke in most studies. Supplementation with folic acid, vitamin B6, and generally lowers homocysteine levels in humans. In a pooled analysis (meta-analysis) of eight randomized trials, folic acid supplementation in varying amounts (usually 0.5 mg to 5 mg per day) reduced stroke risk by 18%.
1 Star
Tinnitus
Refer to label instructions
Vitamin B12 injections may help reduce the severity of tinnitus in people who are deficient in the vitamin.

People exposed to loud noise on the job who develop tinnitus are commonly deficient in . Intramuscular injections of vitamin B12 reduced the severity of tinnitus in some of these people. Injectable vitamin B12 is available only by prescription. The effect of oral vitamin B12 on tinnitus has not been studied.

How It Works

How to Use It

Most people do not require vitamin B12 supplements. However, vegans should supplement with at least 2 to 3 mcg per day.

People with pernicious anemia are often treated with injections of vitamin B12. However, oral administration of 1,000 mcg per day can be used reliably as an alternative to vitamin B12 injections.1, 2, 3, 4, 5

Absorption of vitamin B12 is reduced with increasing age. Some research suggests that elderly people may benefit from 10 to 25 mcg per day of vitamin B12.6, 7, 8 One study of elderly people with vitamin B12 deficiency suggested that as much as 500 to 1,000 mcg of vitamin B12 per day might be necessary to achieve optimal vitamin B12 status.9 Vitamin B12 status was measured in this study using a sensitive laboratory test (the plasma methylmalonic acid concentration).

When vitamin B12 is used for therapeutic purposes other than correcting a deficiency, injections are usually necessary to achieve results.

Sublingual forms of vitamin B12 are available,10 but there is no proof that they offer any advantage to oral supplements.

Where to Find It

Vitamin B12 is found in all foods of animal origin, including dairy, eggs, meat, poultry, and fish. According to one report, small, inconsistent amounts occur in seaweed (including nori and chlorella) and tempeh.11 Many researchers and healthcare professionals believe that people cannot rely on vegetarian sources to provide predictably sufficient quantities of vitamin B12. However, another study found substantial amounts of vitamin B12 in nori (at least 55 mcg per 100 grams of dry weight).12

Possible Deficiencies

Vegans (vegetarians who also avoid dairy and eggs) frequently become deficient, though the process often takes many years. People with malabsorption conditions, including those with tapeworm infestation and those with bacterial overgrowth in the intestines, often suffer from vitamin B12 deficiency. Malabsorption of vitamin B12 can also result from pancreatic disease, the effects of gastrointestinal surgery, or various prescription drugs.13

Pernicious anemia is a special form of vitamin B12 malabsorption due to impaired ability of certain cells in the stomach to make intrinsic factor—a substance needed for normal absorption of vitamin B12. By definition, all people with pernicious anemia are vitamin B12-deficient. They require either vitamin B12 injections or oral supplementation with very high levels (1000 mcg per day) of vitamin B12.

Older people with urinary incontinence14 and hearing loss15 have been reported to be at increased risk of B12 deficiency.

Infection with Helicobacter pylori, a common cause of gastritis and ulcers, has been shown to cause or contribute to adult vitamin B12 deficiency. H. pylori has this effect by damaging cells in the stomach that make hydrochloric acid—which is needed for normal absorption of vitamin B12. In one trial, H. pylori was detected in 56% of people with anemia due to vitamin B12 deficiency. Successful eradication of H. pylori led to improved blood levels of B12 in 40% of those infected.16 Other studies have also suggested a link between H. pylori infection and vitamin B12 deficiency.17, 18 Elimination of H. pylori infection does not always improve vitamin B12 status. People with H. pylori infections should have vitamin B12 status monitored.

In a preliminary report, 47% of people with tinnitus and related disorders were found to have vitamin B12 deficiencies that may be helped by supplementation.19

HIV -infected patients often have low blood levels of vitamin B12.20

A disproportionately high amount of people with psychiatric disorders are deficient in B12.21 Significant vitamin B12 deficiency is associated with a doubled risk of severe depression, according to a study of physically disabled older women.22

A preliminary study found that postmenopausal women who were in the lowest one-fifth of vitamin B12 consumption had an increased risk of developing breast cancer.23

Although blood levels of vitamin B12 may be higher in alcoholics, actual body stores of vitamin B12 in the tissues (such as the liver) of alcoholics are frequently deficient.24, 25

Low blood levels of vitamin B12 are sometimes seen in pregnant women; however, this does not always indicate a vitamin B12 deficiency.26 The help of a healthcare professional is needed to determine when a true vitamin B12 deficiency exists in pregnant women with low blood levels of the vitamin.

Hydroxocobalamin (a form of vitamin B12) has been recognized for more than 40 years as an effective antidote to cyanide poisoning. It is currently being used in France for that purpose. Because of its safety, hydroxocobalamin is considered by some researchers to be an ideal treatment for cyanide poisoning.27

Best Form to Take

Cyanocobalamin, a synthetic form of vitamin B12 commonly found in supplements, is normally present only in trace amounts in the body. It has no known biological activity on its own, and must be converted by the body into active forms of vitamin B12. Supplementing with hydroxocobalamin, another form of vitamin B12, results in more sustained levels of vitamin B12 in the body compared with cyanocobalamin and can be used for conditions such as cyanide poisoning (cyanocobalamin should not be used for cyanide poisoning). Partly for these reasons, hydroxocobalamin is to be preferred as a vitamin B12 supplement over cyanocobalamin. Other acceptable forms of vitamin B12 include methylcobalamin and adenosylcobalamin, although there is no clear evidence that these forms (except in very rare cases) are preferable to hydroxocobalamin.28

Interactions

Interactions with Supplements, Foods, & Other Compounds

If a person is deficient in vitamin B12 and takes 1,000 mcg or more of folic acid per day, the folic acid supplementation can improve the anemia caused by vitamin B12 deficiency. The effect of folic acid on vitamin B12 deficiency-induced anemia is not a folic acid toxicity. Rather, the folic acid supplementation is acting to correct one of the problems caused by B12 deficiency. The other problems caused by a lack of vitamin B12 (mostly neurological) do not improve with folic acid supplements, and can become irreversible if vitamin B12 is not provided to someone who is vitamin B12 deficient.

Some doctors are unaware that vitamin B12 deficiencies often occur without anemia—even in people who do not take folic acid supplements. This lack of knowledge can delay diagnosis and treatment of people with vitamin B12 deficiencies. This can lead to permanent injury. When such a delayed diagnosis occurs in someone who inadvertently erased the anemia of vitamin B12 deficiency by taking folic acid supplements, the folic acid supplementation is often blamed for the missed diagnosis. This problem is rare and should not occur in people whose doctors understand that a lack of anemia does not rule out a vitamin B12 deficiency. Anyone supplementing 1,000 mcg or more per day of folic acid should be initially evaluated by a doctor before the folic acid can obscure a proper diagnosis of a possible B12 deficiency.

Interactions with Medicines

Certain medicines interact with this supplement.

What Are Drug Interactions
Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

Reduce Side Effects

  • Fenofibrate

    Increased blood levels of homocysteine are associated with increased risk of atherosclerosis and heart disease. One study revealed that fenofibrate dramatically increases blood homocysteine levels, though blood levels of vitamins were not reduced. In one study, supplementation with 10 mg per day of folic acid prevented the increase in homocysteine levels resulting from fenofibrate therapy. Further research is needed to determine whether supplemental  vitamin B6 and vitamin B12, which are also capable of lowering homocysteine levels, might lower fenofibrate-induced elevations in homocysteine levels.

  • Gentamicin

    In a study of guinea pigs, a single intramuscular injection of methylcobalamin (a form of vitamin B12), in the amount of 125 mg per 2.2 pounds of body weight, given immediately after administration of gentamicin, prevented damage to the inner ear, which is a common side effect of gentamicin therapy. No studies have been done to determine whether the same protective effect would occur in humans.

  • Phenobarbital

    Anemia is an uncommon side effect experienced by people taking anticonvulsant drugs. Though the cause may be folic acid deficiency in many cases, a deficiency of vitamin B12 may also be a factor in some instances. Deficiencies of folic acid and vitamin B12 can lead to nerve and mental problems. One study revealed that individuals on long-term anticonvulsant therapy, despite having no laboratory signs of anemia, had dramatically lower levels of vitamin B12 in their cerebrospinal fluid (the fluid that bathes the brain) when compared with people who were not taking seizure medications. Improvement in mental status and nerve function was observed in a majority of symptomatic individuals after taking 30 mcg of vitamin B12 daily for a few days. Another study found that long-term anticonvulsant therapy had no effect on blood levels of vitamin B12. Despite these contradictory findings, people taking anticonvulsant drugs for several months or years might prevent nerve and mental problems by supplementing with vitamin B12.

  • Phenytoin

    Anemia is an uncommon side effect experienced by people taking anticonvulsant drugs. Though many researches believe that low blood levels of folic acid are involved, the effects might be caused by a vitamin B12 deficiency. Deficiencies of folic acid and vitamin B12 can lead to nerve and mental problems. One study revealed that individuals on long-term anticonvulsant therapy, despite having no laboratory signs of anemia, had dramatically lower levels of vitamin B12 in their cerebrospinal fluid (the fluid that bathes the brain) when compared with people who were not taking seizure medications. Improvement in mental status and nerve function was observed in a majority of symptomatic individuals after taking 30 mcg of vitamin B12 daily for a few days. Another study found that long-term anticonvulsant therapy had no effect on blood levels of vitamin B12. The results of these two studies indicate that people taking anticonvulsant drugs might experience side effects of vitamin B12 deficiency, and that the deficiency is not easily detected by the usual blood tests. Therefore, individuals taking anticonvulsant drugs for several months or years might prevent nerve and mental problems by supplementing with vitamin B12.

  • Valproate

    Anemia is an uncommon side effect experienced by people taking anticonvulsant drugs. Though the cause may be folic acid deficiency in many cases, a deficiency of vitamin B12 may also be a factor in some cases. Deficiencies of folic acid and vitamin B12 can lead to nerve and mental problems. One study revealed that individuals on long-term anticonvulsant therapy had dramatically lower levels of vitamin B12 in their cerebrospinal fluid (the fluid that bathes the brain) when compared with people who were not taking seizure medications. Improvement in mental status and nerve function was observed in a majority of symptomatic individuals after taking 30 mcg of vitamin B12 daily for a few days. Another study found that long-term anticonvulsant therapy had no effect on blood levels of vitamin B12. Despite these contradictory findings, people taking anticonvulsant drugs for several months or years might prevent nerve and mental problems by supplementing with vitamin B12.

Support Medicine

  • none

Reduces Effectiveness

  • none

Potential Negative Interaction

  • none

Explanation Required

  • Gabapentin

    Anemia is an uncommon side effect experienced by people taking anticonvulsant drugs. Though many researches believe that low blood levels of folic acid are involved, the effects might be caused by a vitamin B12 deficiency. Deficiencies of folic acid and vitamin B12 can lead to nerve and mental problems. One study revealed that individuals on long-term anticonvulsant therapy, despite having no laboratory signs of anemia, had dramatically lower levels of vitamin B12 in their cerebrospinal fluid (the fluid that bathes the brain) when compared with people who were not taking seizure medications. Improvement in mental status and nerve function was observed in a majority of symptomatic individuals after taking 30 mcg of vitamin B12 daily for a few days. Another study found that long-term anticonvulsant therapy had no effect on blood levels of vitamin B12. The results of these two studies indicate that people taking anticonvulsant drugs might experience side effects of vitamin B12 deficiency, and that the deficiency is not easily detected by the usual blood tests. Therefore, individuals taking anticonvulsant drugs for several months or years might prevent nerve and mental problems by supplementing with vitamin B12.

The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

Oral vitamin B12 supplements are not generally associated with any side effects.

Although quite rare, serious allergic reactions to injections of vitamin B12 (sometimes even life-threatening) have been reported.29, 30, 31 Whether these reactions are to the vitamin itself, or to preservatives or other substances in the injectable vitamin B12 solution, remains somewhat unclear. Most, but not all, injectable vitamin B12 contains preservatives.

In a double-blind trial, people with diabetes who also had with kidney disease received a daily placebo or 2.5 mg of folic acid, 1 mg of vitamin B12, and 25 mg of vitamin B6 for three years. Compared with the placebo, vitamin supplementation accelerated the decline in kidney function and increased the incidence of cardiovascular events (such as heart attacks) and heart disease-related deaths.32 Based on this study, diabetics with kidney disease should not take these vitamins without a doctor's supervision.

References

1. Goldberg TH. Oral vitamin B12 supplementation for elderly patients with B12 deficiency. J Am Geriatr Soc 1995;43:SA73 [abstr #P258].

2. Lederle FA. Oral cobalamin for pernicious anemia. Medicine's best kept secret? JAMA 1991;265(1):94-5.

3. Kondo H. Haematological effects of oral cobalamin preparations on patients with megaloblastic anemia. Acta Haematol 1998;99:200-5.

4. Waif SO, Jansen CJ, Crabtree RE, et al. Oral vitamin B12 without intrinsic factor in the treatment of pernicious anemia. Ann Intern Med 1963;58:810-7.

5. Crosby WH. Oral cyanocobalamin without intrinsic factor for pernicious anemia. Arch Intern Med 1980;140:1582.

6. Kaufman W. The use of vitamin therapy to reverse certain concomitants of aging. J Am Geriatr Soc 1955;3:927-36.

7. Lindenbaum J, Rosenberg IH, Wilson PWF, et al. Prevalence of cobalamin deficiency in the Framingham elderly population. Am J Clin Nutr 1994;60:2-11.

8. Verhaeverbeke I, Mets T, Mulkens K, Vandewoulde M. Normalization of low vitamin B12 serum levels in older people by oral treatment. J Am Geriatr Soc 1997;45:124-5 [letter].

9. Eussen SJ, de Groot LC, Clarke R, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dose-finding trial. Arch Intern Med 2005;165:1167-72.

10. Delpre G, Stark P, Niv Y. Sublingual therapy for cobalamin deficiency as an alternative to oral and parenteral cobalamin supplementation. Lancet 1999;354:740-1. [letter]

11. Rauma AL, Torronsen R, Hanninen O, Mykkanen H. Vitamin B12 status of long term adherents of a strict uncooked vegan diet (“living food diet”) is compromised. J Nutr 1995;125:2511-5.

12. Takenaka S, Sugiyama S, Ebara S, et al. Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status. Br J Nutr 2001;85:699-703.

13. Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency. A Guide for the primary care physician. Arch Intern Med 1999;159:1289-98 [review].

14. Rana S, D'Amico F, Merenstein JH. Relationship of vitamin B12 deficiency with incontinence in older people. J Am Geriatr Soc 1998;46:931-2.

15. Houston DK, Johnson MA, Nozza RJ, et al. Age-related hearing loss, vitamin B-12, and folate in elderly women. Am J Clin Nutr 1999;69:564-71.

16. Kaptan K, Beyan C, Ural AU, et al. Helicobacter pylori—is it a novel causative agent in Vitamin B12 deficiency? Arch Intern Med 2000;160:1349-53.

17. Perez-Perez GI. Role of Helicobacter pylori infection in the development of pernicious anemia. Clin Infect Dis 1997;25:1020-2 [review].

18. Fong TL, Dooley CP, Dehesa M, et al. Helicobacter pylori infection in pernicious anemia: a prospective controlled study. Gastroenterology 1991;100:328-32.

19. Shemesh Z, Attias J, Ornan M, et al. Vitamin B12 deficiency in patients with chronic tinnitus and noise-induced hearing loss. Am J Otolaryngol 1993;14:94-9.

20. Remacha AF, Cadafalch J. Cobalamin deficiency in patients infected with the human immunodeficiency virus. Semin Hematol 1999;36:75-87.

21. Lindenbaum J, Healton EB, Savage DG, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med 1988;318:1720-8.

22. Penninx BW, Guralnik JM, Ferrucci L, et al. Vitamin B(12) deficiency and depression in physically disabled older women: epidemiologic evidence from the Women's Health and Aging Study. Am J Psychiatry 2000;157:715-21.

23. Wu K, Helzlsouer KJ, Comstock GW, et al. A prospective study on folate, B12, and pyridoxal 5'-phosphate (B6) and breast cancer. Cancer Epidemiol Biomarkers Prev 1999;8:209-17.

24. Kanazawa S, Herbert V. Total corrinoid, cobalamin (vitamin B12), and cobalamin analogue levels may be normal in serum despite cobalamin in liver depletion in patients with alcoholism. Lab Invest 1985;53:108-10.

25. Cravo ML, Camilo ME. Hyperhomocysteinemia in chronic alcoholism: relations to folic acid and vitamins B(6) and B(12) status. Nutrition 2000;16:296-302 [review].

26. Pardo J, Peled Y, Bar J, et al. Evaluation of low serum vitamin B(12) in the non-anaemic pregnant patient. Hum Reprod 2000;15:224-6.

27. Sauer SW, Keim ME. Hydroxocobalamin: improved public health readiness for cyanide disasters. Ann Emerg Med 2001;37:635-41.

28. Gaby, AR. Nutritional Medicine. Concord, NH: Fritz Perlberg Publishing, 2011.

29. Snowden JA, Chan-Lam D, Thomas SE, Ng JP. Oral or parenteral therapy for vitamin B12 deficiency. Lancet 1999;353:411 [letter].

30. Hovding G. Anaphylactic reaction after injection of vitamin B12. Br Med J 1968;3:102.

31. Moloney FJ, Hughes R, O'Shea D, Kirby B. Type I immediate hypersensitivity reaction to cyanocobalamin but not hydroxycobalamin. Clin Exp Dermatol 2008;33:412-4.

32. House AA, Eliasziw M, Cattran DC, et al. Effect of B-vitamin therapy on progression of diabetic nephropathy. A randomized controlled trial. JAMA 2010;303:1603-9.

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