Clinical Research Directory

Inclusion Criteria: Subjects are able to participate if they: 1. Are 18 years or older. 2. Live in the United States. 3. Are interested in vitamin D as a potential preventive measure against COVID-19 in which they self-administer a daily dose of vitamin D during the 12-month study period. 4. Are willing to complete self-report measures at 5 time points over the course of 12 months by completing a 15-minute survey at intake via web and 10-minute web-based follow-up surveys. Exclusion Criteria: Subjects are excluded from study participation if they: 1. Report being pregnant, planning to become pregnant, and/or report breastfeeding during the study period. 2. Report a history of chronic kidney disease, including a history of abnormal GFR and/or creatinine. 3. Report a history of hyperparathyroidism. 4. Report a history of increased falls. 5. Report a history of hypercalcemia. 6. Report a history of gastrointestinal absorptive disorders, including having undergone bariatric surgery. 7. Report a history of kidney stones (1 in past year or 2 in lifetime). 8. Report already taking more than 400 IU of vitamin D daily as recommended by their health care provider, excluding multivitamins and excluding supplements that include vitamin D and calcium together. 9. Report taking D2. 10. Report a history of sarcoidosis.