Daily oral vitamin D3 regimen in similar cumulative doses is more effective than weekly oral vitamin D3 regimen in patients with vitamin D deficiency

Context: Vitamin D deficiency is a common health problem worldwide, especially in the Middle Eastern region. Although various dosing regimens of vitamin D have been used for the treatment of vitamin D deficiency, it is still unclear as to which dosing regimen can efficiently increase the serum level of vitamin D in different patient population. 
Aim: This study was designed to compare the efficacy of weekly and daily regimens of vitamin D3 in patients with vitamin D deficiency. 
Settings and Design: A randomized clinical trial was conducted in the autumn and winter of 2016 and 2017, Hamadan, Iran. 
Materials and Methods: A total of 130 patients with moderate to severe hypovitaminosis D were allocated into two groups: weekly 50,000 IU (routine recommended dose for vitamin deficiency treatment) or daily 4,000 IU (safe upper limit dose of vitamin D per day) of oral vitamin D3 for 8 and 14 weeks, respectively. The serum levels of 25-OH-vitamin D were measured in all patients at baseline and at the end of the treatment period. 
Results: Results of this study showed that though both dosing regimens can be effective in increasing the serum level of 25-OH-vitamin D, higher percentage of the subjects in the daily regimen group achieved the sufficient serum level of 25-OH-vitamin D when compared to the weekly regimen group. 
Conclusion: Accordingly, probably owing to better bioavailability of daily regimen of vitamin D3 and establishment of a more steady serum concentration compared with weekly regimen, it can be recommended as the preferred dosing regimen for effective treatment of vitamin D deficiency.