1. Patients in the Memphis VA Medical Center with documented vitamin D deficiency, determined by measurements of 25(OH)D3, were recruited for this study. 25(OH)D3 measurements are commonly obtained during routine clinical care in both primary care and nephrology clinics. Patient with a wide range of kidney function, ranging from normal estimated glomerular filtration rate (e GFR) to patients with stage III and V (CKD) (estimated GFR <60 ml/min) were recruited treated with weekly oral administration of 10,000 IU of cholecalciferol for a total of 8 weeks in order to correct the vitamin D deficiency.