Objective: To determine the success rate of the protocol for attaining vitamin D sufficiency and to identify factors that associate with the success of correcting low vitamin D status.

Material and Method: Medical records of patients who sought treatment at the Siriraj Metabolic Bone Disease Clinic between March 2012 and December 2014 were retrospectively reviewed. All patients who had serum 25-hydroxyvitamin D (25(OH)D) levels available at both baseline and three months post-treatment were included. Treatment protocol according to 25(OH)D level was, as follows: 60,000, 40,000, 20,000, and 0 IU per week for patients with baseline serum 25(OH)D level of less than 20, 20 to less than 30, 30 to 40, and more than 40 ng/mL, respectively.

Results: Two hundred and forty-three patients entered the study and 187 patients (77%) had serum 25(OH)D level 30 ng/mL or more, after treatment with our stratified vitamin D2 supplementation protocol. This proportion increased to 98.4% when 20 ng/mL was used as the cut-off value for adequate vitamin D status. In addition, we found body mass index (BMI) and baseline vitamin D level to be associated with attainment of vitamin D sufficiency status after treatment with our vitamin D2 supplementation protocol.

Conclusion: Our stratified vitamin D2 supplementation protocol was effective in attaining vitamin D sufficiency status in approximately 77% of patients. Since baseline vitamin D level and BMI were found to be two important factors that influence the success of treating hypovitaminosis D, these two factors should be considered before and during treatment for low vitamin D level.

Keywords: Vitamin D2, Ergocalciferol, Vitamin D deficiency, Vitamin D insufficiency, Hypovitaminosis D, 25-hydroxyvitamin D