Variations in Serum Vitamin B12 Levels among Metformin Receiving and Non-Receiving Type 2 Diabetes Mellitus Patients - A Case Control Study in a Tertiary Care Hospital in Puducherry

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BACKGROUND Metformin is considered as a cornerstone in the treatment of diabetes and is the most frequently prescribed first line therapy for individuals with T2DM. Metformin use in type 2 diabetes mellitus has shown to cause vitamin B12 (B12) deficiency. Besides these, B12 deficiency related neuropathy may mimic and/or aggravate the underlying diabetic neuropathy. Furthermore, there have been lack of consensus regarding the universal routine screening of serum B12 levels among metformin users with T2DM, and similar studies from India are also limited. So, we wanted to study the relationship between metformin use and serum B12 in T2DM patients. METHODS The study included a total of 104 subjects of which 52 are T2DM affected individuals who are only on metformin therapy for at least 3 months, served as cases and 52 are newly diagnosed T2DM age and sex matched individuals yet to be medically treated, served as controls. Their blood samples were collected to estimate vitamin B12 and other parameters. RESULTS The median B12 levels in cases 213.5 pg/mL (IQR 136.25-301.0) were found to be significantly lower (P < 0.05) when compared to median levels of controls 240 pg/mL (IQR 214-303.25). B12 levels also showed a significant fall in their levels with increasing duration of T2DM. CONCLUSIONS Metformin induced vitamin B12 deficiency plays a major role in developing life risks in T2DM patients. Routine screening and supplementation of B12 may be required in T2DM patients KEYWORDS Metformin, Type 2 Diabetes Mellitus, Vitamin B12