Vitamin B(12) in type 2 diabetic patients treated with metformin.

OBJECTIVE To test vitamin B12 plasma levels in type 2 diabetic patients treated with metformin in our area. METHODS A cross-sectional, observational study of consecutive type 2 diabetic patients on drug treatment attending an internal medicine outpatient clinic. RESULTS One hundred and nine patients (81 treated with metformin) were enrolled into the study. Mean time on metformin treatment was 43.5 months and mean drug dose was 1,779 mg/day. Patients treated with metformin had significantly lower vitamin B(12) plasma levels (393.5 vs. 509 pg/mL, P = .0008). Seven (8.6%) of 81 patients treated with metformin and none of the 28 patients not treated with the drug had vitamin B(12) plasma levels lower than 197 pg/mL. No correlation was found between vitamin B12 plasma levles and metformin treatment time or dosage. CONCLUSIONS In type 2 diabetic patients, treatment with metformin is associated to lower vitamin B12 plasma levels. Vitamin B12 deficiency associated with metformin is relatively common in our area.