Type-2 diabetes is a growing national epidemic with nearly 1.7 million people newly diagnosed each year Vitamin D deficiency is highly prevalent worldwide and is possibly implicated in pathogenesis of DM,the aim of the work is to (1) study vitamin D status in type2 diabetic Egyptian patient,(2) High light the relationship of vitamin D deficiency and T2 DM as well as its vascular complications and its associations (other members of metabolic syndrome ) ,(3) Show the impact of vitamin supplementation on glycemic control , insulin level , insulin resistance , lipid profile and vascular complications of diabetes. The study included 200 type 2 diabetic patients and thirty age and sex healthy participants as controls. history taking, Examination and laboratory investigations HA1C, lipid profile, serum vitamin level, albumin creatinine ratio, fasting insulin were done for every subjects at base line and after six months' supplementation of vitamin D (2000 iu + calcium) daily. serum vitamin D was found to be significantly low in the patient compared to controls, vitamin D supplementation had significant favorable effect on HOMA, HA1C, insulin resistance albumin creatinine ratio, retinopathy and atherosclerotic cardiovascular complications