Vitamin D3 Substitution in Vitamin D Deficient Kidney Transplant Recipients

Inclusion Criteria: * age \> 18 * deceased donor kidney transplant recipients * only kidney transplant recipients * vitamin D deficiency defined as 25 (OH)D \< 50nmol/l Exclusion Criteria: * re-transplantation for the second time if the patient is highly immunized and therefore included in the aphaeresis program * re-transplantation for the third or further time * significant impaired intestinal resorption: malabsorption due to celiac sprue, systemic scleroderma; maldigestion due to chronic pancreatitis, pancreatic insufficiency, pancreas resection, mucoviscidosis, Zollinger-Ellison-syndrome * history of inflammatory bowel disease: Crohn's disease, ulcerative colitis * previous gastrectomy, small bowel or large bowel resection, intestinal bypass surgery * severe liver disease: cirrhosis * HIV positive