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

Background: Vitamin D deficiency is common among patients with type 2 diabetes mellitus and may be associated with inadequate glycemic control.Objective: To determine the association between vitamin D deficiency and poor glycemic control among adults with type 2 diabetes mellitus.Materials and methods: This cross-sectional study was conducted at Lady Reading Hospital (LRH), Peshawar, Pakistan, from March 2024 to February 2025 among 350 adults with type 2 diabetes mellitus.Serum 25hydroxyvitamin D (25(OH)D) and glycated hemoglobin (HbA1c) measurements were obtained from hospital laboratory records.Serum 25(OH)D was measured using an enzyme-linked immunosorbent assay (ELISA), according to the laboratory standard operating procedure.Vitamin D deficiency was defined as a serum 25(OH)D level <20 ng/mL and poor glycemic control was defined as HbA1c ≥7.0%.Data were analyzed using descriptive statistics, the chi-square test, independent-samples t-test, and binary logistic regression.Multivariable binary logistic regression was performed to assess the independent association between vitamin D deficiency and poor glycemic control after adjustment for age, BMI, diabetes duration, hypertension, dyslipidemia, physical inactivity, dietary adherence, medication adherence, previous diabetes education, and smoking.Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were reported.Results: Among 350 participants, 218 (62.29%) were vitamin D deficient and 132 (37.71%) were nondeficient.Poor glycemic control was present in 226 (64.57%) participants, while 124 (35.43%) had adequate control.Vitamin D deficiency was observed in 164 (72.57%) participants with poor glycemic control compared with 54 (43.55%) with adequate control (p <0.001).Participants with poor glycemic control had lower mean serum 25(OH)D levels than those with adequate control (16.72 ± 6.43 vs. 23.84 ± 7.16 ng/mL; p <0.001).After adjustment for the prespecified covariates listed above, vitamin D deficiency was associated with higher odds of poor glycemic control (AOR = 2.87, 95% CI: 1.76-4.68;p <0.001).Conclusion: Vitamin D deficiency was common and was independently associated with higher odds of poor glycemic control among adults with type 2 diabetes mellitus.Given the cross-sectional design, this association should not be interpreted as causal, and prospective studies are needed to clarify the relationship.