Serum Vitamin B12 Level in Patients with Type 2 Diabetes Mellitus on Metformin Therapy and its Impact on Peripheral Nerve Conduction: A Prospective Study.

Metformin is the primary treatment for newly diagnosed T2DM patients. However, Metformin may cause Vitamin B12 deficiency, which may either cause neuropathy or indirectly worsen hyperglycemia-induced neuropathy. Aims of the study was to record the effect of six months of regular metformin therapy on vitamin B12 level and to study the impact of Vitamin 12 on peripheral nerve conduction in response to 6 months of metformin therapy. This was a longitudinal study done in the Department of Physiology in collaboration with the Medicine Department of AIIMS, Bhopal, on 52 newly diagnosed cases of diabetes mellitus. A nerve conduction study was done at the start and at the end of six months using the Nihon Kohden Neuropack X1 Machine. Serum B12, homocysteine (HC), Methyl Malonic acid (MMA), RBS and HbA1c were estimated at the start and at the end of six months. The study involved 52 participants in the range of 38.8-49.0 years (Median- 45 years). Six months of metformin therapy significantly affected Vitamin B12 (decrease), serum HC (increase) and serum MMA levels (increase) (p<0.001). A significant decrease in amplitude and nerve conduction velocity was observed in the motor and sensory nerve conduction study. Significant correlations were seen between Vitamin B12 levels and a number of nerves affected, Serum MMA and Serum HC levels. Six months of metformin therapy had a significant effect on decreasing the level of vitamin B12. No new patient developed neuropathy; however significant decrease in amplitude in motor as well as sensory nerve conduction study was observed which may be due to significant decrement in B12 level. However, further studies are recommended in diabetic patients with large sample sizes and varied durations.