Association Between Vitamin D Status and Glycaemic Control in Patients with Type 2 Diabetes Mellitus

Abstract

Background: Vitamin D deficiency has been increasingly recognized as a potential contributor to impaired glucose metabolism and poor glycaemic control in patients with type 2 diabetes mellitus (T2DM). However, the relationship between vitamin D status and glycaemic control remains inconsistent across different populations.

Objectives: To evaluate the association between serum vitamin D levels and glycaemic control in patients with T2DM and to determine whether vitamin D deficiency is associated with adverse metabolic parameters.

Methods: This hospital-based cross-sectional observational study included 150 adults with T2DM. Demographic, clinical, and biochemical data were recorded. Serum 25-hydroxyvitamin D [25(OH)D], fasting blood glucose (FBS), postprandial blood glucose (PPBS), glycated haemoglobin (HbA1c), and lipid profile were measured. Patients were categorized into vitamin D deficient (<20 ng/mL) and sufficient (≥20 ng/mL) groups. Continuous variables were compared using the independent samples t-test or Mann–Whitney U test, while categorical variables were analysed using the Chi-square test. Pearson correlation and multivariable logistic regression were performed to evaluate the association between vitamin D status and glycaemic control.

Results: Vitamin D deficiency was observed in 62.7% of participants. Patients with vitamin D deficiency had significantly higher HbA1c (9.02 ± 1.48% vs. 7.74 ± 1.19%; p<0.001), FBS (182.6 ± 46.3 vs. 145.2 ± 39.5 mg/dL; p<0.001), and PPBS (262.7 ± 63.4 vs. 214.8 ± 54.1 mg/dL; p<0.001) than those with sufficient vitamin D levels. Vitamin D levels demonstrated a significant inverse correlation with HbA1c (r = −0.48, p<0.001). After adjustment for confounding variables, vitamin D deficiency remained an independent predictor of poor glycaemic control (adjusted OR 3.64; 95% CI: 1.74–7.63; p<0.001).

Conclusion: Vitamin D deficiency was highly prevalent among patients with T2DM and was significantly associated with poorer glycaemic control and an adverse metabolic profile. Routine assessment of vitamin D status may aid in identifying patients at risk of poor metabolic control. Further prospective studies are warranted to determine whether correction of vitamin D deficiency improves long-term glycaemic outcomes.