Ongoing treatment with pharmacologic doses of vitamin D, vitamin D metabolites or analogues Pregnant or lactating women; Severe underlying diseases, such as advanced malignant tumor, end-stage lung disease, etc. History of elevated serum calcium >9.8 mg/dl) Chronic hepatic or renal failure or patients with reduced kidney function, cancers, and malabsorption syndrome, a granulomatous disorders such as Sarcoidosis or Tuberculosis Supplementation with over the counter formulations of vitamin D2 or vitamin D3 Use of tanning bed or artificial UV exposure within the last two weeks. Consuming medication affecting bone metabolism (anti-convulsants, anti-tuberculosis medication, cimetidine, theophylline, and cholestyramine), as well as those who are following special diets such as vegetarian diet or consuming fortified products regularly. Subjects with a history of an adverse reaction to orally administered vitamin D, vitamin D metabolites or analogues. Inability to give informed consent

Ongoing treatment with pharmacologic doses of vitamin D, vitamin D metabolites or analogues Pregnant or lactating women; Severe underlying diseases, such as advanced malignant tumor, end-stage lung disease, etc. History of elevated serum calcium >9.8 mg/dl) Chronic hepatic or renal failure or patients with reduced kidney function, cancers, and malabsorption syndrome, a granulomatous disorders such as Sarcoidosis or Tuberculosis Supplementation with over the counter formulations of vitamin D2 or vitamin D3 Use of tanning bed or artificial UV exposure within the last two weeks. Consuming medication affecting bone metabolism (anti-convulsants, anti-tuberculosis medication, cimetidine, theophylline, and cholestyramine), as well as those who are following special diets such as vegetarian diet or consuming fortified products regularly. Subjects with a history of an adverse reaction to orally administered vitamin D, vitamin D metabolites or analogues. Inability to give informed consent