Metformin Induced Vitamin B12 deficiency: A Cross sectional study. Untangling the connection

Metformin is a widely popular drug to treat type 2 diabetes as it is efficacious, inexpensive and relatively well tolerated with minimal side effect profile. It is known that long term metformin use predisposes a person to develop Vitamin B12 deficiency, however guidelines to screen and treat are yet to be well established. Vitamin B12 deficiency is known to cause peripheral neuropathy and anemia.

Ours is a prospective, observational, cross sectional study based in a hospital setting in a tertiary care center. Study participants were subjected to serum Vitamin B12 analysis and Michigan neuropathy screening instrument was used to screen for peripheral neuropathy.

We report statistically significant association between metformin use and development of Vitamin B12 deficiency. The average duration of metformin use that resulted in development of Vitamin B12 deficiency was 13.6 years. We also found statistically significant association of metformin use with development of peripheral neuropathy.

Long term metformin leading to Vitamin B12 deficiency is common knowledge, however we need more targeted guidelines on when to screen and treat for B12 deficiency. Some subsets of the population such as elderly and vegetarians are more prone and hence we need to educate more physicians and patients on the same.