By the time patients require dialysis replacement therapy, nearly all chronic kidney diseases (CKD) patients are affected with uremic bone diseases. High-turnover osteodystrophy can be prevented; patients with CKD should be monitored for imbalances in calcidiol (25 OH vitamin D), calcium, and phosphate homeostasis. We aimed to determine the effect of a monthly oral 300,000 IU vitamin D(3) (cholecalciferol) supplementation on the uremic bone diseases (UBD) markers such as iPTH and alkaline phosphatase in CKD patients. Among a total of 70 patients under treatment in the nephrology unit, 40 predialysis CKD patients (mean age of 49 +/- 14, male/female 20/20) were included the study. The patients were randomly divided into two groups. Treatment group included 20 patients (mean age of 51 +/- 14, male/female 9/11), and the control group comprised 20 patients (mean age of 47 +/- 14, male/female 9/11). Treatment group patients were given a single dose of Devit3 ampoule (300,000 U cholecalciferol) per month orally way. Patients in the control group did not take any vitamin D for a month. The level of calcidiol was lower than normal range in two groups. After a month, treatment group patient's calcidiol increased statistically significant (6.8 +/- 3.5 to 17.8 +/- 21.4 ng/mL, p < 0.001). After a month, iPTH level decreased in the treatment group statistically significantly (368 +/- 274 to 279 +/- 179 pg/ml, p < 0.001). At the 30(th) day of the treatment, in 9/20 of the treatment group patients (45%), the iPTH value decreased at least 30% (p < 0.001). We suggest that oral depot cholecalciferol treatment causes a statistically significant decrease of serum iPTH level but does not cause a statistically significant change in Ca, P, ratio of Ca x P, or urinary calcium creatinine rate in UBD predialysis CKD. This treatment can be used safely for the predialysis CKD patients, along with the cautious control of serum calcium and phosphor.