Question & Answer

Does taking Vitamin D prevent or treat COVID-19?

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  • There are claims on social media that taking Vitamin D supplements may help treat or prevent COVID-19 infection.
  • There are currently no national (HSE) or international (WHO, CDC) guidelines for the use of Vitamin D to help treat or prevent COVID-19 infection.
  • At the moment, five ongoing randomised controlled trials are looking at whether Vitamin D has a role in preventing and/or treating COVID-19 infection.
  • There is evidence to suggest that people who are very deficient in Vitamin D are more likely to get respiratory tract infections (infections that affect the airways and lungs).
  • A systematic review of 25 randomised trials found that appropriate Vitamin D supplementation was safe, and that it protected against respiratory tract infections. It also found that people who were very Vitamin D deficient got the most benefit.
  • Most people should be able to get the Vitamin D they need by eating a varied and balanced diet and through sun exposure.
  • The HSE website outlines the correct amount of Vitamin D for people who may have Vitamin D deficiency. It is important not to take too much Vitamin D, as this could weaken bones.
  • The recommended level of Vitamin D supplementation according to the HSE website is 25 micrograms (0.025mg) or less a day of Vitamin D supplements. Taking 25 micrograms (0.025mg) or less a day of Vitamin D supplements is unlikely to cause any harm.
  • A recent report on Irish research indicates that:
    • 47% of all adults aged >85 are likely to be deficient in Vitamin D in winter;
    • 27% of the over 70s (who are ‘cocooning’) are likely to be deficient;
    • 1 in 8 (13%) adults over 55 are likely to be deficient in Vitamin D all year.

Things to Remember


  • Lead Researcher: Dr Sandra Galvin, HRB-Trials Methodology Research Network, NUI Galway.
  • Reviewed by: Professor Declan Devane, School of Nursing and Midwifery, HRB-Trials Methodology Research Network, Evidence Synthesis Ireland & Cochrane Ireland, NUI Galway.
  • Evidence Advisor: Dr Frank Moriarty,  Royal College of Surgeons in Ireland (RCSI).
  • Evidence Advisor: Deirdre Mac Loughlin, PPI Ignite, NUI Galway.
  • Journalist Advisor: Dr Claire O’Connell, Contributor, The Irish Times.