Metformin causes vitamin B12 deficiency

Dec 01, 2006

Metformin, which is being used increasingly to treat polycystic ovary syndrome, significantly increases the likelihood of vitamin B12 deficiency, according to the results of a nested case–control study.

Metformin, which is being used increasingly to treat polycystic ovary syndrome, significantly increases the likelihood of vitamin B12 deficiency, according to the results of a nested case–control study.

Researchers from China found that as dose and treatment duration of metformin increase, so does the risk of the vitamin shortage. They calculated that each 1-g/d increase of metformin almost triples the risk of vitamin B12 deficiency (OR 2.88; 95% CI; 2.15–3.87; P<0.001). Those using metformin for 3 years or more were almost two-and-a-half times as likely to develop the deficiency as those receiving the agent for less than 3 years (OR 2.39; 95% CI; 1.46–3.91; P=0.001).

The researchers admit that a shortcoming of the study was the use of serum B12 concentrations alone to define the vitamin's deficiency without metabolite measurements for confirmation. Nevertheless, they believe the findings have important screening, monitoring, and prevention implications for patients taking the drug.