Metformin-Induced Vitamin B₁₂ Deficiency

These researchers examined aspects of metformin use associated with vitamin B₁₂ deficiency. They used a centralized laboratory system to identify 155 patients with vitamin B₁₂ levels <150 pmol/L (<203 pg/mL), elevated HbA_1C levels, and metformin use for at least 1 year, as well as 310 diabetic patients without vitamin B₁₂ deficiency while taking metformin.

After adjustments for confounders, B₁₂ deficiency correlated strongly with metformin dose (odds ratio, 2.88 for each 1-g/day dose increment) and duration (OR, 2.39 for metformin use lasting >3 years vs. <3 years).