Low serum B12 level is a common occurrence in patients with type 2 diabetes (T2DM) treated with metformin. There is lack of evidence concerning blood testing of vitamin B12 and current clinical guidelines make no recommendations on the detection or prevention of vitamin B-12 deficiency during metformin treatment. Our objective was to examine the current practice and clinical determinants of vitamin B12 testing in metformin treated T2DM patients. Data were collected from health maintenance organization patients, and consisted of T2DM patients who were newly prescribed metformin from 2008 to 2013. Patients were randomly divided into two subgroups: referred for a vitamin B12 blood test, and did not receive a referral. The demographic data and medical characteristics were analyzed. 5131 patients began taking metformin during the study period. Of these 2332 (44.5 %) had vitamin B12 tested. Significant differences were found between the groups in regard to glycosylated hemoglobin, low density lipoprotein, systolic blood pressure, dyslipidemia, chronic renal failure, and disease duration. A significant positive association (p < .05) was found between vitamin B12 testing and insulin treatment, retinopathy, neuropathy and hypertension. Vitamin B12 in elderly (>75 years) patients was significantly lower (p < .01). Insulin treatment, hypertension, and chronic diabetic complications in metformin treated T2DM patients are associated with higher rates of vitamin B12 testing. T2DM patients 75 years and above were less likely to be tested for B12 deficiency.
Keywords: Metformin-treated patients; Primary care physician; Vitamin B12 screening.