Inclusion Criteria:  Adults, ages 18-70 years old Either male or female Taking less than 2,000 IU of vitamin D daily as a supplement during the 30 days before starting the study Ability to swallow a pill of typical size or a liquid less than 1 mL daily for 30 days Ability to speak, read, and understand English Access to smart phone or smart device with internet access for study-related communications Ability to do 3 at-home vitamin D finger prick blood tests on 3 separate days. The kits and supplies will be given to you. Ability to drop off finished blood tests at a UPS store or UPS drop box, or schedule a UPS pickup at your home, on each of the same days as you do the blood tests  Exclusion Criteria:  Females who are pregnant Taking, on average, more than 2,000 IU of vitamin D daily within 30 days before the study Currently have COVID-19 infection History of COVID-19 infection or positive COVID-19 test in last 60 days People with a diagnosis of Cystic Fibrosis People with a diagnosis of Crohn's Disease People diagnosed with Celiac Disease People with known diagnosis or history of any kidney related disease Including, but not limited to: Chronic kidney disease; End stage renal disease; Polycystic kidney disease; Lupus nephritis; Kidney cancer, Alport syndrome; Amyloidosis; Goodpasture syndrome; and Wegener's granulomatosis People with known diagnosis or history of any liver related disease Including, but not limited to: Hepatitis A; Hepatitis B; Hepatitis C; Fatty liver disease; Cirrhosis of the liver; Liver cancer; Hemochromatosis; Wilson disease