Effect of vitamin D supplementation on HbA1c level in a cohort of type 1 diabetic patients

Background and objective: Glycemic control is essential to halt the progression of diabetic complications. Some studies previously showed the effect of vitamin D on pancreatic β-cell function and insulin secretion. This study aimed to assess the effect of vitamin D supplementation on HbA1c in patients with type 1 diabetes and vitamin D deficiency. Methods: This prospective quasi-experimental study was conducted in Erbil city from 1st September to 1st December 2019. In this study, 76 patients attending Layla Qasim diabetic center were tested. Only 50 patients were recruited that had vitamin D deficiency (25OHD: <20) and were aged less than 18 years. They received vitamin D supplementation for 12 weeks. HbA1c and vitamin D level was measured before and after supplementation. Results: Before vitamin D supplementation, the mean level of serum 25(OH)D among females (8.67 ± 2.56) was lower than males (14.31 ± 3.19). However, no association was found between the initial HbA1c level and gender. HbA1c level (mean = 8.24 ± 0.49) improved significantly after vitamin D supplementation to the level of 7.93 ± 0.67 (P = 0.032). There was a significant difference between groups of glycosylated hemoglobin levels of (first tertile<7.5%, second tertile 7.6%-9.9%, third tertile ≥10%) after 12 weeks of supplementation with vitamin D (P <0.001). Conclusion: Vitamin D supplementation in type 1 diabetic patients with vitamin D deficiency lead to significant improvement in HbA1c level. Keywords: Diabetes; Deficiency; Vitamin D.