Background: Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycaemia as a result of insulin deficiency, insulin resistance or both. Objective: To assess the impact of vitamin D replacement therapy on glycemic state in type 2 diabetic chronic kidney disease (CKD) patients. Patients and Methods: 70 patients previously diagnosed as type 2 DM (according to guidelines used by National Institute of Health USA) attending Al-Azhar Assuit University Hospital, internal medicine department and outpatient clinics was included in our study where vit. D was replaced in our groups and its impact on glycemic state was analyzed by bivariate and multivariate analyses. Results: Our study is a prospective study revealed a significant negative correlation between 25(OH)D levels and HbA1c values before and after vit. D replacement therapy. Conclusion: Vitamin D replacement therapy had a beneficial effect on glucose hemostasis via a significant reduction in HbA1c, this emphasizes the potential therapeutic implications of vitamin D supplementation as a promising preventative and therapeutic agent for improved glycemic control among type 2 DM patients with CKD