Correlation between Vitamin D and Glycated Hemoglobin (HbA1c) in Patients with Type 2 Diabetes Mellitus: A Single Center Cross-sectional Study

Background: Type 2 diabetes mellitus (T2DM) is a common metabolic disorder, with increasing evidence relating vitamin D deficiency (VDD) to poor glycemic control.Aim: The aim of this study was to assess the correlation between vitamin D levels and Glycated hemoglobin (HbA1c) in patients with T2DM.Materials and Method: This cross-sectional study was directed at Eastern Medical College Hospital, Cumilla, from January to December 2024. A total of 80 T2DM patients, aged 30 to 75 years, were purposively selected. Data were collected using a pre-designed questionnaire, and participants with renal failure or on vitamin D supplements were excluded. After obtaining informed consent, blood samples were collected to measure Fasting Blood Sugar (FBS), HbA1c, and serum vitamin D levels.Results: FBS and HbA1c levels were highest in the vitamin D deficient group (10.9±4.7 mmol/L and 9.1±1.8%, respectively), indicating poorer glycemic control with lower vitamin D levels. Serum creatinine levels were similar across all groups, while serum vitamin D levels decreased from normal (32.2±0.4 ng/mL) to insufficient (23.1±2.2 ng/mL) and deficient (15.2±2.6 ng/mL). Serum VD levels also decreased with falling glycemic control: 22.2±4.5 ng/mL to 19.0±6.2 ng/mL and 18.4±3.8 ng/mL, showing an inverse relationship between HbA1c and vitamin D levels. Serum vitamin D levels were slightly higher in males (20.8±4.7 ng/mL) than females (18.8±5.6 ng/mL). Pearson correlation analysis showed a negative linear relationship between HbA1c and serum vitamin D levels (r= -0.22; p=0.04).Conclusion: The study revealed an immense inverse relation between VD levels and HbA1c in T2DM patients, indicating the potential importance of VD supplementation in glycemic management. J Med Coll Women Hosp.2025; 21 (1):32-37