Association of Vitamin D Deficiency With Glycemic Control in Type 2 Diabetes Mellitus

Background Insulin secretion and glucose metabolism are influenced by vitamin D. Deficiency can lead to a decrease in insulin sensitivity and a deterioration in glycemic control. Objectives This study's objective is to examine the association between serum vitamin D and glycemic control (HbA1c) among patients with type 2 diabetes mellitus (T2DM). Methods We studied 120 patients with T2DM. The measurement of vitamin D (25-hydroxyvitamin D (25(OH)D)) and HbA1c used established methods. Deficiency was classified as having a level of vitamin D < 20 ng/mL. Results Mean age was 52.6 ± 9.4 years; 70/120 (58.3%) were male. Vitamin D deficiency was present in 82/120 (68.3%). Mean HbA1c was higher in deficient vs sufficient patients (8.4 ± 1.2% vs 7.6 ± 1.0%, t = 3.82, p = 0.002). Fasting plasma glucose and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were also higher in the deficient group (p ≤ 0.01). Serum vitamin D correlated negatively with HbA1c (r = -0.34, p = 0.001). Conclusion Vitamin D deficiency was common and associated with poorer glycemic control. Screening and treatment of deficiency may aid metabolic outcomes in T2DM.