Serum vitamin B12 levels and glycemic fluctuation in patients with type 2 diabetes mellitus

PURPOSE: The aim of the study was to explore the correlation between serum vitamin B12 levels and glycemic fluctuation in patients with type 2 diabetes mellitus (T2DM). METHODS: This study included 202 T2DM patients in whom blood glucose levels were recorded using a continuous glucose monitoring system retrospectively. Glycemic fluctuation was determined using the average daily risk range (ADRR), a diabetes-specific measure of the risk for hyper- and hypoglycemia. RESULTS: Serum vitamin B12 levels were higher in T2DM patients with wider glycemic fluctuations than in those with minor glycemic fluctuations (p < 0.001). We observed a positive correlation between serum vitamin B12 levels and ADRR in both T2DM patients who received and did not receive metformin therapy (r = 0.388, p < 0.001 and r = 0.280, p = 0.004, respectively). Multiple linear regression analysis showed that serum vitamin B12 levels were independently correlated with ADRR in T2DM patients who received and did not receive metformin therapy (beta = 0.367, p < 0.001 and beta = 0.410, p < 0.001, respectively). CONCLUSIONS: Serum vitamin B12 levels are correlated with glycemic fluctuation in patients with T2DM and may serve as an underlying useful biomarker of glycemic fluctuation in T2DM patients, treated with or without metformin therapy.