Vitamin D is a commonly available essential prohormone humans need to regulate blood calcium and has recently emerged as potentially helpful in combating severe COVID-19. Despite its importance, some studies estimate as much as 40% of the US population is deficient in vitamin D. Most available vitamin D supplements have little absorption data and are nearly all softgels or capsules. This clinical trial is designed as a preliminary pharmacokinetics study to assess the absorbance of a nano liquid D3 supplement that can be taken as an oral spray once daily. Preliminary evidence suggests that this nano liquid D3 may be absorbed more readily than commercially available softgel dosage forms of D3. This randomized, double-blind, placebo-controlled trial will compare nano liquid D3 to commonly available D3 oral softgels and a placebo control group over the course of a thirty-one (31) day study period.

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

Full blinding protocols employed to mask all participants, all those engaging with participants, and the PI for the duration of the study period.