To investigate the optimal initial and maintenance doses of vitamin D2 supplementation for the treatment of vitamin D insufficiency in Thai adults, and to determine the prevalence of and risk factors for hypovitaminosis D among Thai adults.

A double-blinded prospective, randomized study undertaken at outpatient clinic of King Chulalongkorn Memorial Hospital. The patients with vitamin D insufficiency were included and divided into three groups according to their initial 25OHD concentrations. Patients are randomly assigned to receive vitamin D2 40000, 60000 or 80000 IU once weekly. Serum 25(OH)D levels are measured at 12 weeks after vitamin D2 supplemetaiton. The patients with 25OHD more than 30ng/mL are enroll into the maintenance phase of the study and are randomly assigned to receive vitamin D2 20000 or 40000 IU once weekly for another 12 months. The 25OHD concentration are measure again at the end of the study.

Inclusion Criteria:

1. Adult age ≥ 15 years
2. BMI 18 - 35 kg/m2
3. Serum 25(OH)D < 30ng/ml

Exclusion Criteria:

1. Hypercalcemia, nephrolithiasis, or fractures
2. Hepatic disease
3. Kidney disease
4. Granulomatous disease
5. Currently supplemented with vitamin D