Cholecalciferol loading dose guideline for vitamin D-deficient adults.

INTRODUCTION Severe vitamin D deficiency is very common. Evidence-based guidelines for rapid correction with high-dose oral cholecalciferol are not yet available. OBJECTIVE To develop a practical cholecalciferol loading dose regimen. MATERIALS AND METHODS A total of 208 vitamin D-deficient subjects (serum 25-hydroxyvitamin D(3) (25-OHD(3)) level <50 nmol/l), aged 18-88 years, were treated with solubilized cholecalciferol, 50,000 IU/ml. They received either 25,000 IU every fortnight for 8 weeks (total dose 100,000 IU), 25,000 IU every week for 6 weeks (total dose 150,000 IU), or 25 000 IU every week for 8 weeks (total dose 200,000 IU). Blood samples were collected at baseline and 10 days after the final dose of cholecalciferol. Results Most patients were severely vitamin D deficient: 76% had a serum 25-OHD(3) level <30 nmol/l at baseline. Cholecalciferol in a cumulative dose of 100,000, 150,000, and 200,000 IU increased mean serum 25-OHD(3) level by 29 nmol/l (95% confidence interval (CI): 23-35 nmol/l), 43 nmol/l (95% CI: 36-50 nmol/l), and 69 nmol/l (95% CI: 64-75 nmol/l) respectively. The change in 25-OHD(3) (Delta25-OHD(3)) was related to the dose per kilogram body weight (R(2)=0.38, P<0.0001), and is described by the equation: Delta25-OHD(3)=0.025x(dose per kg body weight). CONCLUSION The cholecalciferol loading dose required to reach the serum 25-OHD(3) target level of 75 nmol/l can be calculated as follows: dose (IU)=40x(75-serum 25-OHD(3))xbody weight.