Kinetics and concentrations of circulating 25-hydroxyvitamin D using different vitamin D repletion regimens

Vitamin D repletion guidelines in Armenia were untested. Adults deficient in vitamin D received supplementation via low dose-high frequency, medium dose-medium frequency, or high dose-low frequency regimens. All achieved vitamin D sufficiency within 12 weeks. Providers may determine the replacement strategy based on patient variables.

Vitamin D deficiency is common throughout the world. While guidelines for vitamin D replacement exist, they have not been tested in Armenia. This study aimed to investigate the efficacy of three administration regimens to replete vitamin D: low dose-high frequency, medium dose-medium frequency, high dose-low frequency.

We recruited community-dwelling adults in Yerevan, Armenia, who were found to be deficient in vitamin D. Participants were subsequently randomized to receive vitamin D via oral drops according to one of three arms: (A) 7000 IU daily for 12 weeks followed by 3500 IU daily for 24 weeks; (B) 50,000 IU weekly for 12 weeks followed by 25,000 IU weekly for 24 weeks; and (C) 100,000 IU every other week for 12 weeks, followed by 50,000 IU every other week for 24 weeks. After 36 weeks, all subjects received the same amount of vitamin D. Circulating levels of 25(OH)D were measured at baseline, and at weeks 4, 8, 12, 24, and 36.

The mean baseline 25(OH)D level of the 60 adults who participated in the study (average age 44.8, 80% female) was 19.4 ng/mL. All three arms showed statistically significant increases in 25(OH)D levels from baseline to 4 weeks, and again from 4 to 8 weeks, following which levels plateaued at the mid-40s ng/mL. At baseline, group A had a slightly higher mean 25(OH)D level than group B (21.0 vs 16.9 ng/mL, p-value 0.03) as well as at week 36 (47.7 vs 40.2 ng/mL, p-value 0.007); otherwise, there were no significant differences between the groups at any other time points.

This study supports a recommendation that different dosing regimens of vitamin D replacement will reach similar desirable levels when steady state is reached at weeks 12 and 36, thus enabling healthcare providers an option to determine the most appropriate replacement strategy based on individual patient preference and other variables.