This randomized controlled trial examined the relationship between therapeutic doses of vitamin D and improvement of glycemic parameters in female patients with Type 2 Diabetes Mellitus (T2DM). 27 female patients with T2DM, aged 38-64 years, were randomly assigned to intervention (n=15) and control (n=12) groups at the endocrinology department of Tripoli Medical Center from 2015 to 2023. The intervention group received 50,000 IU vitamin D (cholecalciferol) weekly for 12 weeks, while controls received a placebo. Serum levels of 25-hydroxyvitamin D [25(OH)D], fasting blood glucose (FBG), HbA1c, lipid profile, and calcium were measured before and after intervention. Data were analyzed using SPSS version 20 with paired t-tests and correlation analyses. Statistical significance was set at p<0.05. Baseline vitamin D deficiency was prevalent: 47.0% of patients had severe deficiency, 41% moderate deficiency, and only 11.0% had sufficient levels. After 12 weeks of supplementation, 88% of patients demonstrated improved vitamin D levels. Mean serum 25(OH)D increased significantly from 12.50±12.40 nmol/L to 37.00±10.00 nmol/L (p<0.05). Approximately 80% of patients exhibited decreased HbA1c (from 9.20±1.80% to 7.90±1.70%; p<0.05). A significant inverse correlation was observed between post-intervention HbA1c and 25(OH)D levels (r = -0.354, p=0.040). Fasting blood glucose improved from 174.44±63.77 mg/dL to 144.51±38.90 mg/dL. No significant changes occurred in the control group. Weekly vitamin D supplementation (50,000 IU) for 12 weeks significantly improved vitamin D status and glycemic control in female patients with T2DM, demonstrating an inverse relationship between vitamin D and HbA1c levels. Vitamin D supplementation may be a beneficial adjunct therapy for glycemic management in vitamin D-deficient diabetic patients.