Can vitamin d stop COVID-19? large trial tests high doses
NCT ID NCT04536298
First seen Jun 26, 2026 · Last updated Jun 26, 2026
Summary
This large study tested whether high-dose vitamin D3 supplements could help people recently diagnosed with COVID-19 avoid severe illness and also prevent the virus from spreading to their household members. Over 2,000 participants across the U.S. and Mongolia took either vitamin D or a placebo for 4 weeks. The goal was to see if vitamin D reduces healthcare visits and infections in close contacts.
What this could mean
Our plain-language read of the trial. This is informational only — not medical advice or a prediction.
- Active substance
- vitamin D3 (cholecalciferol) dietary supplement
- What this could lead to
- If it works, this could point toward a simple, low-cost way to reduce COVID-19 severity and prevent household spread.
- What could go wrong
- This is a completed Phase 3 trial, but vitamin D's effect on COVID-19 has been mixed in other studies. High doses may cause side effects like kidney stones.
This is an AI summary of the original study and may miss details. Read our disclaimer.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
-
Brigham and Women's Hospital
Boston, Massachusetts, 02215, United States
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Other studies related to the condition(s) this trial covers.
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