Objective: The aim of this study was to determine the effects of vitamin D supplementation on kidney function, blood concentrations of 25-hydroxyvitamin D, and parathyroid hormone levels.

Methods: The 25-hydroxyvitamin D levels of approximately 4,000 participants between the ages of 18 and 75 years were investigated retrospectively. Inclusion criteria included screening 25-hydroxyvitamin D <10 ng/mL at the local clinical laboratory. This study required the control of blood parameters at 2 and 6 weeks. Because of this, 120 patients were chosen and categorized according to treatment procedures. The first group of participants was prescribed a fixed dose of 300,000 IU oral vitamin D filled at local clinical pharmacies. The second group of participants was prescribed a fixed dose of 300,000 IU parenteral vitamin D filled at local clinical pharmacies. The last group of participants was prescribed a fixed dose of 50,000 IU once weekly oral vitamin D once weekly for six weeks filled at local clinical pharmacies. Vitamin D values and biochemical laboratory parameters were recorded and were compared between groups using statistical methods.

Results: The treatment regimens with 25-hydroxyvitamin D3 were divided equally among three patient groups (n1=40, n2=40, n3=40). The findings were that 25-hydroxyvitamin D levels changes in the first (p=0.001) and third groups (p=0.001) were greater than the second group (p<0.01).

Conclusion: These effects occur with significant changes in oral vitamin D supplementation rather than when vitamin D is administered parenterally.