Serum B12 Levels in Type II Diabetics on Metformin Therapy and its association with Clinical Neuropathy

Holay MP, Vyawahare M, Shekar K


Background: Metformin use in type II DM has also been known to cause B12 deficiency in as reported many studies. Iatrogenic neuropathy caused by Metformin induced B12 deficiency can add to burden of peripheral neuropathy that already exists in diabetic patients.

Aims and Objectives: 1)To determine the serum vitamin B12 levels in patients of type II DM on metformin therapy and compare it with those not on metformin therapy; 2) To correlate serum vitamin B12 levels with dose and duration of metformin therapy; 3) To investigate association between peripheral neuropathy and serum vitamin B12 levels.

Method: The present two year hospital based cross sectional study enrolled total 132 cases of type 2 diabetes mellitus and divided into two groups, (“metformin” group 70 and “non-metformin” group 62). Serum vitamin B12 levels were measured in all patients. Toronto clinical scoring system (TCSS) and nerve conduction velocity (NCV) tests were used to assess peripheral neuropathy. The correlations of vitamin B12 levels with Toronto clinical score, nerve conduction studies, cumulative dose and duration of metformin therapy was done.

Results: The serum vitamin B12 levels were significantly lower in patients who consumed metformin (292.64 ± 152.82 pg/ml) as compared to non-metformin, (406.91 ± 126.59 pg/ml) group. There was a significant negative correlation of serum vitamin B12 levels with cumulative dose and duration of metformin therapy. The incidence of neuropathy by TCSS and NCV test was significantly higher in metformin group with a positive correlation with cumulative dose and duration of metformin and a negative correlation with serum vitamin B12 levels.

Conclusion: Metformin use is significantly associated with decrease in vitamin B12 levels and increased incidence of neuropathy, this is dependent on dose and duration of metformin therapy.


Metformin, Vitamin B12, Diabetes mellitus (DM), Peripheral neuropathy, Toronto clinical scoring system (TCSS), Nerve conduction velocity (NCV)

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