Impact of Vitamin D Supplementation on HbA1c Levels in Type 2 Diabetes Mellitus Patients with Asymptomatic Vitamin D Deficiency: A Prospective Study.

Original Article

Abstract

ABSTRACT

Background: Vitamin D deficiency is highly prevalent among patients with type 2 diabetes mellitus (T2DM) and has been associated with impaired insulin secretion, increased insulin resistance, and poor glycemic control. Emerging evidence suggests that vitamin D supplementation may improve metabolic outcomes in diabetic patients; however, findings remain inconsistent across different populations and study settings.

Objective: To evaluate the effect of vitamin D supplementation on glycated hemoglobin (HbA1c) levels in patients with T2DM and asymptomatic vitamin D deficiency.

Methods: This prospective interventional study was conducted at the Department of Diabetes, Endocrinology and Metabolic Diseases, Hayatabad Medical Complex, Peshawar, Pakistan, from January 2023 to January 2024. A total of 250 patients with T2DM and serum vitamin D levels below 20 ng/mL were enrolled, of whom 128 completed follow-ups. Participants were allocated into two groups: Group A received metformin therapy alone, while Group B received metformin plus oral vitamin D supplementation (200,000 IU monthly for three months). HbA1c and serum vitamin D levels were measured at baseline and after three months. Data were analyzed using SPSS version 24.0, and a p-value <0.05 was considered statistically significant.

Results: Among the 128 participants analyzed, baseline characteristics were comparable between groups. Patients receiving vitamin D supplementation demonstrated a significantly greater reduction in HbA1c levels compared with those receiving metformin alone (p<0.05). Serum vitamin D concentrations increased significantly in the intervention group, whereas no meaningful changes were observed in the control group.

Conclusion: Vitamin D supplementation significantly improves glycemic control in T2DM patients with asymptomatic vitamin D deficiency and may serve as a beneficial adjunct to standard antidiabetic therapy.