Medication Adherence Monitoring Trial Using Smart Clinical Trial Application and Smart Watch

Inclusion Criteria: * Adults aged 19-64 years at the consent * 25(OH) vitamin D \< 10 ng/mL * Not taking vitamin D at the screening * Fully understood the study procedures Exclusion Criteria: * Hypercalciuria, sarcoidosis * Clinically significant hypersensitivity reaction to Vitamin D * History of or current kidney stone * One of the following findings: 1. Serum calcium level \> upper limit of normal 2. Estimated glomerular filtration rate \< 60 mL/min/1.73m\^2 * Galactose intolerance, Lapp lactase deficiency, Glucose-galactose malabsorption * Unable to use smart clinical trial application or smart watch * Expected to take vitamin D from 4 weeks before the first administration and until the last administration