Brand Name: Glucophage®
Metformin is a drug used to lower blood sugar levels in people with non-insulin-dependent (type 2) diabetes.
Summary of Interactions with Vitamins, Herbs, and Foods
(for details about the summarized interactions, read the full article)
May be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them. Folic acid*
May be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication. Calcium
Avoid: Reduced drug absorption/bioavailability—Avoid these supplements when taking this medication since the supplement may decrease the absorption and/or activity of the medication in the body. Guar gum*
Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results. Ginkgo biloba
Check: Other—Before taking any of these supplements or eating any of these foods with your medication, read this article in full for details. DHEA
Supportive interaction None known
An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
Metformin Interactions with Dietary Supplements
Metformin has been reported to increase blood levels of DHEA-sulfate in at least two studies.1 2
Folic acid and Vitamin B12
Metformin therapy has been shown to deplete vitamin B12 and sometimes, but not always,3 folic acid as well.4 This depletion occurs through the interruption of a calcium-dependent mechanism. Supplementation with calcium has reversed this effect in a clinical trial.5 People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.
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.6 Whether this interaction has clinical importance remains unclear.
In a small, controlled study, guar gum plus metformin slowed the rate of metformin absorption.7 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.
Metformin Interactions with Herbs
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.8 Individuals taking oral anti-diabetes medication should consult a doctor before taking Ginkgo biloba.
Metformin Interactions with Foods and Other Compounds
Food interferes with metformin absorption.9 10 11 Taking metformin with food can reduce the absorption of the drug. Therefore, metformin should be taken an hour before or two hours after a meal unless stomach upset occurs.
Lactic acidosis is a rare but serious side effect of metformin. Alcohol increases the production of lactic acid caused by metformin, increasing the risk of lactic acidosis.12 People taking metformin should avoid alcohol or consult with their doctor before consuming alcohol.
Now I am only confused about one thing: do you take or avoid Iron with Metformin??