Diabetes mellitus is a group of metabolic disorders characterized by chronic hyperglycemia with disturbances in carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, action or both. There is evidence that vitamin D deficiency leads to glucose intolerance and predisposes to type 2 diabetes mellitus. On the other hand, observational studies demonstrated high prevalence of vitamin D deficiency in patients with Type I diabetes mellitus (T1DM) and suggested a contributory role in the pathogenesis of T1DM, while the restoration of vitamin D levels may reduce the risk...