Currently, there’s no cure or treatment for COVID-19. No studies have investigated the effect of vitamin D supplements or vitamin D deficiency on the risk of contracting the new coronavirus that causes COVID-19.

Still, multiple studies have shown that vitamin D deficiency can harm immune function and increase your risk of developing respiratory illnesses.

Additionally, some studies have indicated that vitamin D supplements can enhance immune response and protect against respiratory infections overall.

A recent review that included 11,321 people from 14 countries demonstrated that supplementing with vitamin D decreased the risk of acute respiratory infections (ARI) in both those who were deficient in vitamin D and those with adequate levels.

Overall, the study showed that vitamin D supplements reduced the risk of developing at least one ARI by 12%. The protective effect was strongest in those with low vitamin D levels.

Moreover, the review found that vitamin D supplements were most effective at protecting against ARI when taken daily or weekly in small doses and less effective when taken in larger, widely spaced doses.

Vitamin D supplements have also been shown to reduce mortality in older adults, who are most at risk for developing respiratory illnesses like COVID-19.

Keep in mind that there’s no scientific evidence that taking supplemental vitamin D can protect you from developing COVID-19. However, being deficient in vitamin D may increase your susceptibility to overall infection and disease by harming immune function.

This is especially worrisome given that many people are deficient in vitamin D, especially older individuals who are most at risk of developing more serious COVID-19-related complications.

For these reasons, it’s a good idea to have your healthcare provider test your vitamin D levels to determine whether you have a deficiency in this important nutrient.

Depending on your blood levels, supplementing with 1,000–4,000 IU of vitamin D per day is typically sufficient for most people. However, those with low blood levels will often require much higher doses to increase their levels to an optimal range.

Though recommendations on what constitutes an optimal vitamin D level vary, most experts agree that optimal vitamin D levels lie between 30–60 ng/mL (75–150 nmol/L).

Evidence that vitamin D supplements reduce the risk of developing COVID-19 is lacking, but having healthy vitamin D levels can enhance immune health. Plus, vitamin D supplements may protect against respiratory infections in general