Age \< 18

25D \> 20 ng/ml at time of screening

Clear signs of infection at time of screening (coughing, sneezing, wheezing, frequency, dysuria)

History of conditions that would influence intestinal absorption of vitamin D3 or 25OHD3 supplements

History of nephrolithiasis, primary hyperparathyroidism, or other metabolic bone disease

History of chronic kidney disease (defined as CrCl \< 30 ml/min)

History of rheumatologic or autoimmune conditions

History of sarcoidosis

History of active or latent tuberculosis

History of HIV

History of hyperthyroidism

History of chronic glucocorticoid use defined as the equivalent of 5 mg of prednisone per day for more than 2 months within the last 6 months

History of use of medications known to affect calcium/vitamin D metabolism, bone metabolism, and immune response

Hypercalcemia

Hypercalcinuria

Effects of Vitamin D3 Versus 25OHD3 on Mineral Metabolism and Immune Function