The argument for supplementation

Direct research on vitamin D and Covid

Supplementation studies


  • A parallel pilot randomized open label trial of 76 patients in Spain found that the administration of calcifediol reduced ICU admission and mortality. Of the 50 patients treated with calcifediol. 13/26 patients in the control group required ICU care compared with 1 in the intervention group. (Castillo et all, August 2020)


  • A small cohort trial found that just 16% of patients who received vitamin D, magnesium, and vitamin B12 required oxygen compared with 61.5% of the previous cohort who did not receive DBM supplementation. (Chuen Wen Tan, June 10 2020)
  • A retrospective study found that hospitalized patients who were treated with vitamin D were less likely to die than those who did not receive vitamin D. (Ling et all, October 2020)
  • A quasi-experimental study found that French nursing home residents who had recently received a bolus dose of vitamin D were more likely to survive a Covid-19 infection than residents who had not recently received a supplement. 92% of the 57 people who received vitamin D survived, while 66% of the 9 people in the cooperator group survived. (Anweller et. al, October 2020)

Covid severity associated with serum vitamin D levels

Pre-infection blood samples

Supports link to vitamin D

  1. A retrospective cohort study found that Chicago patients who were likely vitamin D deficient were more likely to test positive for Covid-19. (Meltzer et al, May 2020)
  2. An Israeli study of 7,000 patients with pre-Covid serum vitamin D tests found that vitamin D levels were associated with Covid infection and hospitalization. (Eugene Merzon et al, July 2020)
  3. An analysis of Israeli vitamin D tests performed between 2010 and 2019 found that vitamin D deficiency predicted Covid-19 infection. (Israel et al, August 2020)
  4. An analysis of 190,000 patients found that the probability of testing positive was associated with vitamin D levels. This association held across all age groups, ethnicities and geographies. (Kaufman et all, Sept 2020)

Does not support vitamin D link

  • Vitamin D levels between 2006-2010 were associated with Covid-19 mortality, but not after controlling for other variables in the data set. It’s hard to make inferences from 10 year old blood samples because there’s a causal story in which low vitamin D in 2010 increases vitamin D in 2020 because that group is likely to supplement. (Hastie et al, July 2020)

Post-infection blood samples

Supports vitamin D link

  1. A re-analysis of 107 Swiss blood samples found that PCR positive patients had 25-hydroxyvitamin D concentrations half that of PCR negatives. This finding held after stratifying for age and gender. (Avolio et 1) l, April 2020)
  2. Hospitalized male Covid-19 patients were found to have lower vitamin D levels than controls. (De Smet et al, May 2019)
  3. A observational study from Belgium found that vitamin D deficiency is correlated with the risk for hospitalization for COVID-19 pneumonia and predisposes to more advanced radiological disease stages. (De Smet, May 2020)
  4. Vitamin D deficiency was more common among ITU Covid patients than the general population in a Newcastle hospital. (Panagiotou et all, June 2020)
  5. A Mexican study found that patients with vitamin D serum levels bellow 8 ng/mL had 3.68 higher risk of dying from COVID-19. (Arturo Rodríguez Tort et al, April 2020)
  6. A Iranian study (Maghbooli et al, September 2020) found there was a significant association between vitamin D sufficiency and reduction in clinical severity.
  7. A study of 42 COVID-19 patients in a respiratory ICU found that 50% of vitamin D deficient patients died after 10 days compared with 5% of non-deficient patients. (Carpagnano et all, August 2020)
  8. A prospective cohort study found that vitamin D deficiency was more common among Covid positive patients presenting with Covid symptoms than Covid negative patients, and suggested that it could be considered as a diagnostic tool. (Baktash V et all, August 2020)
  9. A study of patients presenting with Covid symptoms at an Iranian hospital found that vitamin D deficiency and ACE dysregulation were more common among those who tested positive for Covid-19. (Mardenia et all, August 2020)
  10. A German Study found that vitamin D status was associated with need for mechanical ventilation and death. (Radujkovic et al, August 2020)
  11. A small prospective cohort study of older adults found that vitamin D deficiency was associated with mechanical ventilation, but not death. (Baktash et all, September 2020)
  12. A Turkish study found that vitamin D deficiency was associated with mortality. (Karahan & Katkat October 2020)
  13. A study of UK health professionals found that vitamin D deficient individuals were more likely to be seropositive for Covid antibodies. (Aduragbemi et all, October 2020)
  14. A study of Covid positive children found that children with Covid had lower vitamin D levels than healthy controls. (Yilmaz & Sen, October 2020)
  15. A case control study in China found that vitamin D deficiency was higher in Covid patients than healthy controls, and that it was associated with disease severity. (Ye et. al, October, 2020)

Does not support link to vitamin D

  • A small trial did not find an association between vitamin D deficiency and Covid-19 severity. The study did find an association among younger patients. (Macaya et. all, September 2020)

In vitro evidence

  • Calcitriol, the active form of Vitamin D is active against the SARS-COV2 virus. (Chee Keng Mok et al, June 2020)

Non-clinical causal data

  • Evidence supports a vitamin-D causal model more than an acausal one. (Davies et al, June 13 2020)
  • A Mendelian randomisation analysis of excess COVID-19 mortality of African-Americans in the US suggests that vitamin D is a risk factor for Covid Mortality. (Martin Kohlmeier, May 2020)
  • A Mendelian randomization using genes associated with vitamin D deficiency did not support a causal connection between vitamin D and Covid-19 mortality. It appears that this study used UK Biobank data, but the date of the samples were not disclosed. (Liu et al, August 2020)

Ecological studies

  • A study out of Northwestern University found that the vitamin D status of a country’s elderly population was associated with the number of severe cases of Covid-19 in that country. (Daneshkhah1 et al, April 2020)
  • There was a strong correlation between vitamin D levels and European mortality which increased over time. (Chuen Wen Tan, June 2020)
  • UVB radiation, which the skin uses to manufacture vitamin D is associated with lower death rates and case fatality rates. (Moozhipurath et al, May 1st 2020)
  • Covid-19 deaths-per-million appears to vary by latitude. (Rhodes et al, June 2020)
  • Latitude was not associated with a proportional increase in cases during one week of March. (Jüni et al, June 2020)
  • Latitude is a significant predictor of Covid mortality after controlling for age. (Rhodes et al, July 2020)
  • Vitamin D levels were inversely associated with cases per million in Europe, but not with deaths per million. (Sing, Kaur, Kumar Sigh, August 2020)

Vitamin D background and previous studies

Governments recommending Vitamin D

Lit reviews and clinical guidance

If you only have time for one review

Other reviews