This study will test the hypothesis that 6 months of periodic high dose Vitamin D3 replacement (200,000 and 100,000 units cholecalciferol, oral liquid drops at 6 to 8 week intervals) followed in-between by daily 1000 units, decreases insulin resistance by HOMA2-IR ≥ 0.36, in comparison to control, standard dose Vitamin D3 1000IU/ day for 6 months, in south Asians with both Vitamin D deficiency (defined as 25 Hydroxy vitamin D < 25nmol/l) and insulin resistance (defined as HOMA1 -IR≥ 1.93).