Drug Information
Common brand names:
PrandimetSummary of Interactions with Vitamins, Herbs, & Foods
Types of interactions:BeneficialAdverseCheck
Replenish Depleted Nutrients
- 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.
- 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
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
- 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.
- Vitamin B3 (Niacin)
Supplementation with large amounts of niacin (also called nicotinic acid) can increase blood glucose levels in diabetics, which might interfere with the blood-sugar-lowering effects of repaglinide. The form of vitamin B3 known as niacinamide does not have this effect. People who start or stop supplementing niacin while on repaglinide should carefully monitor their blood sugar levels and consult their prescribing doctor about making adjustments in the daily amount of drug taken.
- White Willow
Willow bark contains salicin, which is related to aspirin. Both salicin and aspirin produce anti-inflammatory effects after they have been converted to salicylic acid in the body. Taking aspirin together with repaglinide enhances the blood-sugar-lowering effects of the drug, which might result in unwanted side effects. Controlled research is needed to determine whether taking willow bark together with repaglinide might produce similar effects.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
Explanation Required
- 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.
- DHEA
Metformin has been reported to increase blood levels of DHEA-sulfate in at least two studies.
- 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.
