Context: Hypovitaminosis D appears to be on the rise in young children, with implications for skeletal and overall health.

Objective: To compare the safety and efficacy of vitamin D2 daily, vitamin D2 weekly, and vitamin D3 daily, combined with supplemental calcium, in raising serum 25-hydroxyvitamin D (25(OH)D) and lowering parathyroid hormone (PTH) concentrations.

Design: Six-week randomized controlled trial.

Setting: Urban pediatric clinic in Boston.

Subjects: Forty otherwise healthy infants and toddlers with hypovitaminosis D (25(OH)D < 20 ng/mL).

Interventions: Participants were assigned to one of three regimens: 2000 IU oral vitamin D2 daily, 50,000 IU vitamin D2 weekly, or 2000 IU vitamin D3 daily. Each was also prescribed elemental calcium (50 mg/kg/day). Infants received treatment for 6 weeks.

Main Outcome Measures: Before and after treatment, serum measurements of 25(OH)D, PTH, calcium, and alkaline phosphatase.

Results: All treatments approximately tripled the 25(OH)D concentration. Pre-planned comparisons were non-significant: daily vitamin D2 vs weekly vitamin D2 (12% difference in effect, p=0.66) and daily D2 vs daily D3 (7%, p=0.82). The mean serum calcium change was small and similar in the three groups. There was no significant difference in PTH suppression.

Conclusions: Short-term Vitamin D2 2000 IU daily, vitamin D2 50,000 IU weekly, or vitamin D3 2000 IU daily yield equivalent outcomes in the treatment of hypovitaminosis D among young children. Therefore, pediatric providers can individualize the treatment regimen for a given patient to ensure compliance, given that no difference in efficacy or safety was noted between these three common treatment regimens.