Kinetics and concentrations of circulating 25-hydroxyvitamin D using different vitamin D repletion regimens.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 41369768 · doi:10.1007/s00198-025-07782-w
What was done
Sixty community-dwelling adults with vitamin D deficiency in Yerevan, Armenia (mean age 44.8 years, 80% female) were randomized to one of three cumulative-dose-matched oral drop regimens over 36 weeks: (A) daily dosing (7,000 IU/day for 12 weeks, then 3,500 IU/day for 24 weeks); (B) weekly dosing (50,000 IU/week for 12 weeks, then 25,000 IU/week for 24 weeks); or (C) biweekly dosing (100,000 IU every 2 weeks for 12 weeks, then 50,000 IU every 2 weeks for 24 weeks). Circulating 25(OH)D concentrations were measured at baseline and at weeks 4, 8, 12, 24, and 36.
What was found
Mean baseline 25(OH)D was 19.4 ng/mL. All three arms showed statistically significant increases in 25(OH)D from baseline to 4 weeks and 4 to 8 weeks, plateauing in the mid-40s ng/mL. All groups achieved sufficiency within 12 weeks. Group A had a higher mean 25(OH)D level than Group B at baseline (21.0 vs 16.9 ng/mL, p = 0.03) and at week 36 (47.7 vs 40.2 ng/mL, p = 0.007); no other significant differences between groups were reported at other time points.
Why it matters
This study shows that daily, weekly, and biweekly vitamin D dosing strategies yield similar circulating 25(OH)D concentrations at steady state when cumulative doses are identical, permitting flexible dosing schedules based on patient preference.
Limits
The sample size was small (n = 60 total, ~20 per arm) and predominantly female (80%) from a single geographic region. Baseline 25(OH)D differed significantly between groups A and B. The abstract reports no clinical endpoints (such as fractures or bone density) or safety/toxicity metrics.
Cited by
- contradicts High weekly bolus doses of vitamin D (20,000 to 50,000 IU) exhibit higher absorption efficiency and less supplement concentration variability than daily dosing.