Association of Serum Vitamin B12 Levels with Duration of Metformin Therapy in Type 2 Diabetes Mellitus

Abstract

Background: Metformin is widely prescribed for the management of type 2 diabetes mellitus (T2DM); however, prolonged therapy has been associated with impaired vitamin B12 absorption. This study aimed to evaluate the association between serum vitamin B12 levels and duration of metformin therapy in patients with T2DM.

Materials and Methods: This hospital-based, observational, cross-sectional study included 130 patients with T2DM receiving metformin for at least six months. Participants were categorised according to treatment duration into Group I (less than 2 years), Group II (2–5 years) and Group III (more than 5 years). Serum vitamin B12 concentrations were measured and classified as deficient (below 200 pg/mL), borderline (200–300 pg/mL) or normal (above 300 pg/mL). Group-wise comparisons and correlation analyses were planned using appropriate statistical tests.

Results: In the dataset, the mean age was 54.6 ± 10.8 years, with 56.2% males. Vitamin B12 deficiency was observed in 23.8% of patients, while 30.8% had borderline concentrations. Mean serum vitamin B12 levels progressively decreased across Groups I, II and III (402 ± 112, 326 ± 105 and 241 ± 96 pg/mL, respectively; p<0.001). Deficiency prevalence increased from 7.9% to 19.6% and 41.3% across the respective groups (p<0.001).

Conclusion: The findings suggest an association between prolonged metformin therapy and reduced serum vitamin B12 concentrations. Periodic assessment may facilitate early identification of deficiency among patients receiving long-term treatment.