Urinary calcium response to high dose vitamin D3 with calcium supplementation in patients with multiple sclerosis

Objective: To characterize the effect of vitamin D3 intake on urinary calcium:creatinine ratios across predefined ranges of serum 25(OH)D. Design: Patients with multiple sclerosis (n=25) received escalating doses of vitamin D3 (4000‐40,000IU/d) with calcium (1200mg/d). Results: Urinary calcium:creatinine was driven by increased 25(OH)D when concentrations were < 75. nmol/L (r = 0.424, p = 0.009) and > 200. nmol/L (r = 0.281, p = 0.01), but no relationship existed when 25(OH)D concentrations were 76‐200. nmol/L. Conclusions: A "safe", physiological range of 25(OH)D concentrations is 75‐200. nmol/L. 2011 The Canadian Society of Clinical Chemists.