Drug Information
Common brand names:
Metaglip
Summary of Interactions with Vitamins, Herbs, & Foods
Types of interactions:
Beneficial
Adverse
Check
Replenish Depleted Nutrients
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Vitamin B12
Metformin therapy has been shown to deplete vitamin B12, and sometimes, but not always, folic acid as well. This depletion occurs through the interruption of a calcium-dependent mechanism. People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.
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Folic Acid
Metformin therapy has been shown to deplete vitamin B12, and sometimes, but not always, folic acid as well. People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
Reduces Effectiveness
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In a small, controlled study, guar gum plus metformin slowed the rate of metformin absorption. In people with diabetes this interaction could reduce the blood sugar–lowering effectiveness of metformin. Until more is known, metformin should be taken two hours before or two hours after guar gum–containing supplements. It remains unclear whether the small amounts of guar gum found in many processed foods is enough to significantly affect metformin absorption.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
Potential Negative Interaction
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Ginkgo
In a preliminary trial, administration of Ginkgo biloba extract (120 mg per day) for three months to patients with type 2 diabetes who were taking oral anti-diabetes medication resulted in a significant worsening of glucose tolerance. Ginkgo did not impair glucose tolerance in individuals whose diabetes was controlled by diet. Individuals taking oral anti-diabetes medication should consult a doctor before taking Ginkgo biloba.
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Fenugreek
In a randomized study of 15 patients with type 1 (insulin-dependent) diabetes, fenugreek (Trigonella foenum-graecum) (100 grams per day for ten days) was reported to reduce blood sugar, urinary sugar excretion, serum cholesterol, and triglycerides, with no change in insulin levels, compared with ten days of placebo. In a study of 60 people with type 2 diabetes, fenugreek (25 grams per day for 24 weeks) was reported to significantly reduce blood glucose levels. People using glipizide should talk with their doctor before making any therapy changes.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
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Gymnema
Herbs such as Gymnema sylvestre will often improve blood-sugar control in diabetics.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
Explanation Required
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Chromium
Chromium supplements have been shown to improve blood sugar control in people with diabetes. Consequently, supplementing with chromium could reduce blood sugar levels in people with taking metformin, potentially resulting in abnormally low blood sugar levels (hypoglycemia). While chromium supplementation may be beneficial for people with diabetes, its use in combination with metformin or with any other blood sugar-lowering medication should be supervised by a doctor.
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DHEA
Metformin has been reported to increase blood levels of DHEA-sulfate in at least two studies.
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Magnesium
In a study of patients with poorly controlled type 2 diabetes, low blood levels of magnesium, and high urine magnesium loss, metformin therapy was associated with reduced urinary magnesium losses but no change in low blood levels of magnesium. Whether this interaction has clinical importance remains unclear.
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 new supplement with your doctor or pharmacist.
