Health authorities are already warning of a second wave of COVID-19 in the fall, which means the time to start addressing your vitamin D level is NOW.

We also have a pandemic of vitamin D deficiency, as more than 1 billion individuals worldwide, across all age groups, are deficient in vitamin D.1,2,3,4 Vitamin D deficiency has now been identified as a significant risk factor for positive COVID-19 status,5,6 severe COVID-19 infection7,8,9,10 and death thereof.11,12 I discuss this in "Vitamin D Is Directly Correlated to COVID-19 Outcome."

In one study,13,14 which looked at data from 780 hospital patients in Indonesia, those with a vitamin D level between 20 nanograms per milliliter (ng/mL) and 30 ng/mL had a sevenfold higher risk of death than those with a level above 30 ng/mL. Having a level below 20 ng/mL was associated with a 12 times higher risk of death.

To improve your immune function and lower your risk of viral infections, you'll want to raise your vitamin D to a level between 60 ng/mL and 80 ng/mL by fall. In Europe, the measurements you're looking for are 150 nmol/L and 200 nmol/L. If vitamin D levels were increased in the global population, tens of thousands of people may be saved if or when COVID-19 reemerges.

While prospective controlled studies demonstrating vitamin D's effectiveness in COVID-19 are still lacking, there are many such studies underway. You can review the status of these trials on clinicaltrials.gov.15 As of early June 2020, more than 20 studies had been launched to investigate the benefits of vitamin D against COVID-19.