LAUSR

Background Hypovitaminosis D can be observed in most fragility hip fracture patients. However, measurement of 25-hydroxyvitamin D (25(OH)D) level is costly and may not be available in some centers. Without the baseline serum 25(OH)D level, the appropriate dose of vitamin D supplementation is not known. The aim of this study was to evaluate the effectiveness and safety of vitamin D supplementation in fragility hip fracture patients compared between high- and low-dose vitamin D supplementation. Methods A total of 140 patients diagnosed with fragility hip fracture were randomly allocated to either the high-dose (60,000 IU/week) or low-dose (20,000 IU/week) vitamin D2 supplementation group for 12 weeks. The number of patients who achieved optimal vitamin D level (serum 25(OH)D  >  30 ng/mL), the proportion of patients who developed hypercalcemia, and the functional outcome were compared between groups. Results Of the 140 patients who were enrolled, 21 patients were lost to follow-up during the study period. The remaining 119 patients (58 and 61 in the high- and low-dose groups, respectively) were included in the final analysis. The high-dose group had a higher rate of serum 25(OH)D restoration to optimal level than the low-dose group (82.8% vs 52.5%, respectively; p  < 0.001). Approximately 3.4 and 1.6% of patients in the high- and low-dose groups, respectively, had mild transient hypercalcemia, but none developed moderate, severe, or symptomatic hypercalcemia. There were no differences in functional outcome scores between groups. Conclusions In treatment settings where baseline serum 25(OH)D level can’t be evaluated in older adults with fragility hip fracture, we recommend high-dose vitamin D2 of approximately 60,000 IU/week for 12 weeks, with subsequent switch to a maintenance dose. This regimen effectively restored serum vitamin D to an optimal level in 82.8% of patients without causing symptomatic hypercalcemia. Trial registration The protocol of this study was retrospectively registered in the Thai Clinical Trials Registry database no. TCTR20180302007 on 20 February 2018.