“Is Vitamin D Deficiency a Risk Factor for COVID-19?” Know Your Vitamin D Level

Joseph R. Anticaglia MD
Medical Advisory Board

In a previous article, I touted the benefits of Vitamin D. I wrote: “Besides helping the intestinal absorption of calcium and bone health, there are other benefits of maintaining the vitamin D level within a normal range.

Population studies suggest, according to Dr. Sundeep Khosla of Mayo Clinic, that vitamin D plays a role in:

  • Protecting us against heart disease
  • Lessening the risk of getting cancer
  • Vitamin D might increase cognitive function
  • Could be useful in patients with depression
  • May lower the risk of diabetes
  • Might decrease the risk of autoimmune disease
  • Vitamin D might reduce COVID-19 infections, hospitalizations & deaths.

The above and other studies suggest that vitamin D deficiency places you at increased risk for chronic diseases. This deficiency is prevalent throughout the US and particularly among African Americans and Hispanics. What’s troublesome is the possible linkage between vitamin D deficiency and COVID-19.


In a letter to Mayo Clinic on June 6, 2020, the authors wrote, “Considering the studies on the role of vitamin D in the prevention of acute respiratory infections, supplementation of vitamin D may be reasonable also for the prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and reducing morbidity and mortality in COVID-19 high-risk patients.”

On December 7, 2020 scientists signed an open letter extoling the benefits of Vitamin D in combating COVID-19. The letter proclaimed that higher vitamin D blood levels modulate-interact with many aspects of immune function. The higher blood levels of this vitamin result in lower rates of COVID-19 infections.

The signatories of the December letter claim there’s a reduced risk of COVID hospitalization, a decreased incidence of deaths and one is less likely to be treated in Intensive Care Units (ICUs). Plus, safety data show that taking vitamin D has a very low risk of side effects.

The letter went on to say: “vitamin D’s influence on COVID-19 is very likely causal, not just correlation.” However, there is “push-back” from other scientists about the efficacy of treating COVID-19 patients with vitamin D Deficiency


In answering the question, “Can Vitamin D Protect Against COVID-19?” William F. Marshall, III M. D. wrote, “There isn’t enough data to recommend use of vitamin D to prevent infection with the virus that causes COVID-19 or to treat COVID-19, according to the National Institutes of Health and the World Health Organization,”

However, Dr. Marshall cited studies that that found people with a vitamin deficiency were more likely to test positive for COVID-19. He referred to another study in which individuals who tested positive for the coronavirus with acute respiratory failure did much better with high dose Vitamin D treatment. On the other hand, he named clinical trials that contradicted the usefulness of this vitamin in the prevention and treatment for COVID-19. With these conflicting findings, what’s the takeaway?

Takeaway — ‘Check your vitamin D level. Keep it within a normal range’… Vitamin D is an important component of numerous biochemical actions in the body. Vitamin D deficiency often coexists with COVID-19. It’s helpful to include in your annual physical examination, or sooner, a laboratory test to evaluate this vitamin.

Vitamin D deficiency is a “modifiable” risk factor for many diseases that you can readily and inexpensively control. Supplement with vitamin D3 if you have a deficiency of this vitamin


  1. Joseph R. Anticaglia, MD Vitamin D — Are You Getting Enough? Doctor’s Column, HC Smart, 2019
  2. William F. Marshall; Can Vitamin D Protect Against the Coronavirus Disease (COVID-19) Mayo Clinic, October 20, 2020
  3. NIH; Vitamin D July 27, 2020
  4. Kurt A. Kennel, et al; Vitamin D Deficiency in Adults: When to Test and How to Treat; Mayo Cllin Proc, Aug 2020
  5. Mayo Clinic Proceedings; Letter to the Editor, June 6, 2020
  6. Joseph Mercola et al; Evidence Regarding Vitamin D and Risk of COVID-19 and Its Severity; Nutrients, 2020
  7. Kimberly Forrest; Prevalence and Correlates of vitamin D Deficiency in US Adults; Nutr Res. January, 2020

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.