Publication Description
Context: Vitamin B12 deficiency may occur with metformin treatment, but few studies have assessed risk with long-term use. Objective: To assess risk of B12 deficiency with metformin use in the DPP/DPPOS Design: Secondary analysis from DPP/DPPOS. Participants were assigned to placebo (n=1082, PLA) or metformin (n=1073, MET) for 3.2 years; MET received open-label metformin for an additional 9 years. Setting: 27 study centers in the US Patients: DPP eligibility: elevated fasting glucose, impaired glucose tolerance, and overweight/obesity. Analytic population: participants with available stored samples. B12 levels were assessed at 5 (n=857, n=858) and 13 years [n=756, n=764] in PLA and MET, respectively. Interventions: Metformin 850 mg twice daily versus placebo (DPP); open-label metformin in MET (DPPOS) Main Outcome Measures: B12 deficiency, anemia, peripheral neuropathy Results: Low B12 (≤203 pg/ml) occurred more often in MET than PLA at 5 years (4.3% vs 2.3%, p=0.02) but not at 13 years (7.4% vs. 5.4%, p=0.12). Combined low and borderline-low B12 (≤298 pg/ml) was more common in MET at 5 (19.1% vs 9.5%, p