Associations between metformin use and vitamin B12 levels, anemia, and neuropathy in patients with diabetes: a meta-analysis.

Metformin use led to significantly lowered vitamin B12 concentrations and significantly higher risk of vitamin B12 deficiency in diabetic patients. More quality studies are needed to explore the associations between metformin use and anemia and neuropathy in these patients. Annual vitamin B12 assessment in diabetic patients taking metformin is recommended.