Background: Metformin induced impaired vitamin B12 absorption leading to fall in serum cobalamin levels has been described in literature as early as 1971. Approximately 10% of patients and in some studies 30% of patients on metformin therapy developed metformin related cobalamin deficiency. The risk of cobalamin deficiency is comparatively more among patients with vegetarian diet than in non vegetarians. So, the objectives of the our project were to study the serum vitamin B12 levels in type 2 diabetic patients on long term metformin monotherapy and to study the relationship of serum B12 levles to dietary habits. Methods: A total of 45 patients were chosen by using available database of patients with type 2 diabetes mellitus on metformin monothearapy or insulin and metformin. These patients were asked to visit the hospital by contacting them through telephone. By using a pilot tested proforma, details were collected on demographic data, dietary habits. Duration of treatment with metformin and dose of metformin was also noted. After taking their informed consent, 5 ml of blood was collected and sent to the central laboratory for active vitamin B12 estimation. Thirty age sex matched non diabetic controls were also chosen, who also underwent serum B12 estimation. Results: Our results showed that mean B12 of patients in study group and control group was 50.62pml (picomoles)/dl and 40.66pml/dl respectively (p= 0.301). The sub group analysis showed that mean B12 levels was significantly lower among vegetarian cases (37.25pml/dl) and controls (18.08pml/dl) compared to non vegetarians. Conclusion: Our study shows that long term metformin monotherapy is not a risk factor for development of vitamin B12 deficiency. Vegetarians are at higher risk of B12 deficiency, irrespective of metformin use and non vegetarians are well protected.
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