Vitamin D Repletion in Chronic Kidney Disease

Inclusion Criteria: Inclusion Criteria for Healthy volunteers * Males and post-menopausal females, between the age of 50 -80. * Vitamin D 25-OH level less than 20 ng/ml Inclusion Criteria for Medium-level Kidney Function volunteers * Males and post-menopausal females, between the age of 50 -80. * Chronic kidney disease stage 3 * Vitamin D 25-OH level less than 20 ng/ml Exclusion Criteria: * Serum calcium level \>10.5 mg/dl * Serum phosphorus level \> 5.5 mg/dl * Serum PTH level \< 35 pg/ml * Active infection including HIV, Hepatitis B or C * History of recent acute infection ( within 1 month) * Gastrointestinal disease resulting in significant GI dysfunction or malabsorption * Hgb\< 10 g/dL * Current use of Coumadin * Current use of Vitamin D \>400 IU/day * Current use of systemic steroids or other immunosuppressants * History of malignancy not in remission (\>6 months) * History of current ethanol abuse or illicit drug use * History of significant emotional disorder within the past 5 years * Participation in an investigational drug study within one month of screening * Have any other condition, which in the opinion of the investigator, should prohibit the participation in the study