Question & Answer

Does taking Vitamin D prevent COVID-19?

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  • Our bodies need Vitamin D. We get this vitamin in foods where it occurs naturally, and from foods and drinks that have been fortified with Vitamin D. We also get Vitamin D from sunlight acting on our skin and from supplements such as Vitamin D pills, liquids or sprays.
  • 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 on using Vitamin D supplements to help treat or prevent COVID-19 infection.
  • At the moment, 35 active 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). However, a recent review of the evidence concluded that the authors ‘did not find enough, good‐quality evidence to judge whether vitamin D is an effective or safe treatment for adults with COVID‐19’.
  • 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. It is important not to take too much Vitamin D, as in high doses this could weaken bones, but taking 25 micrograms (0.025mg) or less a day of Vitamin D supplements is unlikely to cause any harm.
  • Most people should be able to get the Vitamin D they need by eating a varied and balanced diet and through sun exposure.
  • A systematic review published in 2017 of 25 randomised trials found that appropriate Vitamin D supplementation was safe, and that it protected against respiratory tract infections overall. It also found that people who were very Vitamin D deficient at the start of the randomised trials benefitted the most from Vitamin D supplements.
  • A recent report on Irish research indicates that:
    • 47% of all adults aged 85 or older are likely to be deficient in (i.e. not have enough of) Vitamin D in winter;
    • 27% of the over 70s (who have been ‘cocooning’ during the COVID-19 pandemic) are likely to be deficient in Vitamin D;
    • 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.