Serum Vitamin B12 Levels among Type 2 Diabetic Patients Maintained on Metformin Based Oral Anti-Diabetic Drugs - An Observational Study


  • Menzies School of Health Research, Translational Senior Research Officer, Darwin, 0810, Australia
  • St. John’s National Academy of Health Sciences, Internal Medicine, Bangalore, Karnataka, 560 034, India
  • University of Mysore, Department of Studies in Food Science and Nutrition, Mysore, Karnataka, 570 006, India


The study was aimed to assess the serum vitamin B12 status of diabetic patients managed on metformin mono or combination therapy. A total of 45 patients (25 males; 20 females) diagnosed with type 2 diabetes for less than 3 years were enrolled into the study. Two groups were formed - metformin monotherapy or Gp1 (21 patients, mean age = 42.8 ± 6.82 years) and combination therapy group or Gp2 (24 patients, mean age = 42.6 ± 7.05 years). It was a self-control study wherein their serum vitamin B12 was measured at baseline (initial) and after 6 months (final). Demographic profile was obtained at baseline. Dietary intake of vitamin B12 was assessed by 3 days recall, while clinical manifestations of B12 deficiency and metformin dosages were obtained at initial and final period. Mean dietary intake of vitamin B12 was 1.16 ± 1.01 μg/day at baseline and 1.25 ± 1.15 μg/day at the sixth month, in the two groups. The mean serum B12 levels of group 1 and 2 at baseline were 347.54 ± 146.10, 293.47 ± 90.90 pg/ml, respectively and those at sixth month were 296.24 ± 144.45 and 239.32 ± 89.90 pg/ml respectively. The mean reduction in serum B12 was 51 and 54 pg/ml in Gp1 and Gp2 respectively, during the six-month observation period and the difference was statistically significant (P = Gp-1; 0.001, Gp-2; 0.002). An inverse relation was found between serum B12 and dosage of metformin. The proportion of patients with weakness, tingling/numbness in hands/feet increased markedly in the sixth month in both the groups. Patients on metformin, both alone or in combination, need monitoring and appropriate management of B12 deficiency.


Type 2 Diabetes Mellitus (T2DM), Oral Antidiabetic Drugs (OADs), Metformin Mono Therapy, Metformin Combination Therapy, Serum B12.

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