OBJECTIVE We aimed to evaluate the vitamin D status, the effect of cholecalciferol supplementation, and the factors associated with vitamin D restoration in nondialytic patients with chronic kidney disease (CKD).

DESIGN The present study was a prospective open-label trial.

SETTING This study took place at the Seoul National University Boramae Medical Center.

SUBJECTS Patients with nondialytic CKD (estimated glomerular filtration rate [eGFR] 10-59 mL/min per 1.73 m(2)) participated in this study.

INTERVENTION Vitamin D status in 210 CKD patients was assessed and the patients with vitamin D deficiency (<30 ng/mL) were administered cholecalciferol (1,000 IU/day) for 6 months.

MAIN OUTCOME MEASURE The restoration rate of vitamin D deficiency at 3 and 6 months and the response-related factors were analyzed.

RESULTS The prevalence of vitamin D deficiency was 40.7% in CKD Stage 3, 61.5% in Stage 4, and 85.7% in Stage 5. The subgroup with vitamin D deficiency had a greater proportion of patients with diabetes, lower eGFR, and higher proteinuria. With the supplementation, 52 patients (76.5%) reached levels of 25-hydroxy vitamin D (25(OH)D) of 30 ng/mL or greater at 3 months, and the restoration of vitamin D was observed in 61 patients (89.7%) at 6 months. Lower levels of 25(OH)D and a higher amount of proteinuria at baseline were the factors associated with lower response to vitamin D supplementation.

CONCLUSION Vitamin D deficiency rate was high in nondialytic CKD patients, and the proportion increased as renal function decreased. A higher amount of proteinuria was the independent risk factor of nonresponse with supplementation. Vitamin D was replenished in most patients with cholecalciferol supplementation without any significant adverse effects.