Abstract:Objecitve To investigate the associations of serum 25-hydroxyvitamin D [25-(OH)D] level with blood glucose and islet β-cell function and the effect of alfacalcidol tablets in patients with type 2 diabetes mellitus (T2DM). Methods A total of 106 patients with T2DM treated in outpatient from November 2017 to March 2019 were enrolled and divided into study group and control group(n=53, each). Blood samples were taken to determine the levels of 25-(OH)D, glycosylated hemoglobin (HbA1c), islet β-cell function index (HOMA-β) and insulin resistance index (HOMA-IR), and the correlations of 25-(OH)D with HbA1c, HOMA-β, HOMA-IR were statistically analyzed. Insulin glargine combined with salgliptin tablets was given in control group, and alfacalcitol tablets were added in study group based on the regimen of control group.The treatment lasted for 2 months in both groups. The levels of HbA1c, fasting plasma glucose (FPG), 2 h postprandial blood glucose (2hPG), fasting insulin (FINS), HOMA-β, HOMA-IR and 25-(OH)D before and after treatment and adverse reactions were compared between two groups. Results 25-(OH)D was significantly negatively correlated with HbA1c and HOMA-IR and was positively correlated with HOMA-β (all P<0.05). After treatment, the levels of HbA1c, FPG, 2hPG and HOMA-IR were significantly lower in study group than those in control group (P<0.05), and levels of FINS and HOMA-β were higher than those in control group(P<0.05). Compared with control group, 25-(OH)D level increased significantly in study group at 4-and 8-week after treatment(P<0.05). There was no significant difference in the incidence of adverse reactions between two groups (11.32% vs 7.55%, P>0.05). Conclusion In T2DM patients, 25-(OH)D level is negatively correlated with HbA1c and HOMA-IR and positively correlated with HOMA-β.Alfacalcidol tablets can improve vitamin D level, blood glucose level and islet β-cell function with safety and reliability.