Vitamin D & COVID-19

Over the past year and a half, vitamin D has emerged as a powerful player in the fight against COVID-19. The following is a compilation of recent research highlighting the important role vitamin D plays in how our bodies respond to SARS-CoV-2, the virus that causes COVID-19.

COVID-19 Severity and Vitamin D Status

As the world seeks solutions to tackle COVID-19, brand new research highlights the importance of vitamin D for reducing the risks associated with respiratory infections caused by coronaviruses. Data published in May 2020 on 212 patients hospitalized with COVID-19 revealed that the severity of infection was correlated to the patient’s vitamin D levels. More than 85 percent of patients with normal vitamin D (≥ 30 ng/ml) experienced mild cases, while 73 percent of patients with vitamin D deficiency (≤ 20 ng/ml) experienced “severe or critical” infections.

Vitamin D is a critical player in immune function and supports immune competence in two important ways. First, it is necessary for the production of antiviral peptides in the respiratory tract, making the respiratory tract less likely to be infected with a virus. Second, it helps promote a balanced inflammatory immune response. According to the researchers, “Vitamin D can help reduce the inflammatory response to SARS-CoV-2 infection, which has a positive effect on patients’ outcome, as an excessive inflammatory response can lead to systemic manifestations that increase severity and complications of the disease.”1 2

Optimal Vitamin D Levels Reduce Risk of COVID Infection & Severe Illness

Can a simple foundational supplement like vitamin D protect you from COVID-19? Recent research says yes. Multiple studies published in 2020 show that having optimal levels of vitamin D reduces your risk of COVID-19 infection and protects against severe COVID-19 outcomes if you do get infected.

In one study, published in the journal PLOS ONE in September 2020, researchers looked at 191,000 blood samples from all 50 states for COVID-positive patients. The researchers discovered that rates of COVID infection were higher in those patients with vitamin D levels less than 20 ng/mL (this is considered deficient) compared to those with levels of 30 ng/mL and higher. Those who were deficient had a positivity rate of 12.5 percent, while people with vitamin D levels of 30-34 ng/mL had a positivity rate of 8 percent and the patients with vitamin D levels higher than 55 ng/mL had a positivity rate of 5.9 percent.

The researchers wrote, “SARS-CoV-2 positivity is strongly … associated with circulating 25(OH)D levels, a relationship that persists across latitudes, races/ethnicities, both sexes, and age ranges. Our findings provide impetus to explore the role of vitamin D supplementation in reducing the risk for SARS-CoV-2 infection and COVID-19 disease.”

Another study investigated whether vitamin D levels affected how sick a person got if they did catch COVID-19. Researchers studied two groups of COVID patients for six weeks—one group included patients who were asymptomatic and the other group included patients who were severely ill and required ICU admission. The asymptomatic patients had a mean vitamin D level of 27.89 ng/mL and the critically ill patients had a mean level of 14.35 ng/mL. The vitamin D-deficient patients had higher levels of inflammation and a higher fatality rate (21% vs 3%) compared to those with the higher vitamin D levels, leading the researchers to “recommend mass administration of vitamin D supplements to populations at risk for COVID-19.”3 4 5

Two New Studies Show Boosting Vitamin D Levels Leads to Better Outcomes in COVID-19

COVID-19 is known to make a real mess of the immune system, suppressing some parts and over-activating others. This is known as immune dysregulation. Meanwhile, vitamin D is known as an immunomodulator, i.e., it’s capable of balancing the immune system by downregulating overactive immune responses and upregulating underactive immune responses. This is why a 2021 study investigated the impact of oral supplementation with high-dose vitamin D (60,000 IUs) daily on balancing immune markers in patients with “mild to moderate” COVID-19 and low vitamin D levels.

The subjects were randomized to receive either a high dose of vitamin D for eight to 10 days or a placebo. Results showed that vitamin D treatment significantly balanced many markers of the dysregulated immune response, including a “highly significant reduction” of inflammatory markers. The authors concluded that this high-dose vitamin D therapy can be safely added to the existing treatment protocols of COVID-19 patients for improved outcomes. Moreover, the above study shows that correcting insufficient vitamin D levels is crucial to maintaining immune competence in the age of COVID-19.

Another 2021 study confirms this conclusion by showing that having optimal vitamin D levels is associated with a decreased risk of mortality from COVID-19 in elderly patients and patients without obesity. This study was performed on COVID-19 patients 18 years and older hospitalized at Boston University Medical Center and compared serum vitamin D levels with COVID-19 outcomes. Results showed that in patients over 65 years, vitamin D sufficiency (≥30ng/mL) was significantly associated with decreased odds of death, acute respiratory distress syndrome, and severe sepsis and/or septic shock. Additionally, among patients with a non-obese BMI (<30 kg/m2) vitamin D sufficiency was significantly associated with a decreased risk of death.6 7

Don’t know your vitamin D levels?  Now is the time to get them checked. Unable to get them checked anytime soon? Supplementing with vitamin D has been shown to be a safe, affordable, and effective way to support optimal vitamin D levels.


  1. Grant, W. B., Lahore, H., Mcdonnell, S. L., Baggerly, C. A., French, C. B., Aliano, J. L., & Bhattoa, H. P. (2020). Evidence That Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. doi:10.20944/preprints202003.0235.v2
  2. First Data to be Published on COVID-19 Severity and Vitamin D Levels. (2020). Retrieved May 04, 2020, from…
  3. Kaufman HW, Niles JK, Kroll MH, Bi C, Holick MF. SARS-CoV-2 positivity rates associated with circulating 25-hydroxyvitamin D levels. PLoS One. 2020 Sep 17;15(9):e0239252. doi: 10.1371/journal.pone.0239252.
  4. Jain A, Chaurasia R, Sengar NS, Singh M, Mahor S, Narain S. Analysis of vitamin D level among asymptomatic and critically ill COVID-19 patients and its correlation with inflammatory markers. Sci Rep. 2020 Nov 19;10(1):20191. doi: 10.1038/s41598-020-77093-z.
  5. Pilz S, Zittermann A, Trummer C, Theiler-Schwetz V, Lerchbaum E, Keppel MH, Grübler MR, März W, Pandis M. Vitamin D testing and treatment: a narrative review of current evidence. Endocr Connect. 2019 Feb 1;8(2):R27-R43. doi: 10.1530/EC-18-0432.
  6. Lakkireddy M, Gadiga SG, Malathi RD, et al. “Impact of daily high dose oral vitamin D therapy on the inflammatory markers in patients with COVID 19 disease.” Sci Reports. 2021, May 20
  7. Charoenngam N, Shirvani A, Reddy N, Vodopivec DM, Apovian CM, Holick MF, Association of vitamin D status with hospital morbidity and mortality in adult hospitalized COVID-19 patients, Endocrine Practice (2021), doi: