Vitamin Interactions with Metformin

Metformin belongs to a group of drugs known as biguanides. It is often prescribed to lower blood sugar in diabetics. This class of drugs lowers blood sugar by affecting its absorption from the intestines, production in the liver and improving the effectiveness of insulin. Metformin, like many drugs, can interact with certain nutrients in the body. This is known as a drug-nutrient interaction, and nutrition education specialist Janice Herman of Oklahoma State University states that these interactions can lead to nutritional deficiencies or change the effectiveness of the drug.

Vitamin B12

Vitamin B12 is probably the most well-known nutrient to interact with the drug Metformin. The B12 in food is unavailable until the acid and enzymes in the stomach release it from its bound form. Once free, B12 combines with a substance known as intrinsic factor and is absorbed from the intestines into the bloodstream. The National Institutes of Health Dietary Supplement Fact Sheet notes that vitamin B12 is found naturally in many foods, especially red meat. The 2006 Age and Ageing journal notes that the absorption of B12 from the intestines is calcium dependent and Metformin lowers blood sugar by affecting calcium. The Age and Ageing journal notes that B12 deficiencies and B12 anemias have been observed in people taking Metformin. Additionally, when they stopped taking the drug, B12 malabsorption resolved itself. suggests that routine blood vitamin B12 levels be measured at two- to three-year intervals while on Metformin.


Calcium was concluded to be the mechanism for the B12 deficiency associated with Metformin. The Age and Ageing journal states that the deficiency can be reversed by simply taking an additional calcium supplement with the prescribed dose of Metformin. The 2000 Diabetes Care journal notes that a dose of 1.2g of calcium carbonate reversed this deficiency when given for a one-month period.

Folic Acid

There appears to be a drug-nutrient interaction between folic acid and Metformin. The mechanism of action is not yet fully understood and occurs to a lesser extent than B12. But it is significant for women of childbearing age who take Metformin and increases an important risk factor for heart disease. Many women with polycystic ovarian syndrome, or PCOS, are prescribed Metformin. PCOS shows many of its symptoms during adolescence and into a woman’s mid-20s. A low level of folic acid before pregnancy is a risk factor for spinal cord defects, like spina bifida, in the unborn child. High homocysteine is an independent risk factor for the development of atherosclerosis and heart disease. The International Journal of Medicine and Medical Science 2009 article concluded that Metformin increases homocysteine levels, especially in males. When 1mg of folic acid per day was taken with Metformin, the rise in homocysteine was prevented.


Chromium is a trace mineral that is needed only in small concentrations in the body. The University of Maryland Medical Center notes that few people are deficient in this nutrient but that as many as 90 percent of Americans are lower than they should be. Chromium helps the body use insulin more effectively and maintain normal blood sugar levels. Chromium is a popular supplement for blood sugar regulation among diabetics and non-diabetics. The University of Maryland Medical Center states that chromium may enhance the effectiveness of diabetes medications like Metformin. It notes that chromium supplements taken with Metformin may cause blood sugar levels to drop too low and that people taking this medication may require lower doses of the drug due to the added effect.