Many recent studies have looked at the impact of vitamin D on COVID-19.
One study found that people who had a vitamin D deficiency were more likely to test positive for the virus that causes COVID-19 than people who had normal levels of vitamin D.
Other research observed high rates of vitamin D deficiency in people with COVID-19 who experienced acute respiratory failure.
And a small, randomized study found that of 50 people hospitalized with COVID-19 who were given a high dose of a type of vitamin D (calcifediol), only one needed treatment in the intensive care unit. In contrast, among the 26 people with COVID-19 who weren't given calcifediol, 13 needed to be treated in the intensive care unit.
Vitamin D deficiency is also more common in people who are older, people who have a body mass index of 30 or higher (obesity), and people who have high blood pressure (hypertension). These factors also increase the risk of severe COVID-19 symptoms.
Yet, here 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 World Health Organization.
Further research is needed to determine what role, if any, vitamin D and vitamin D deficiency might play in the prevention of and treatment of COVID-19.
In the meantime, if you have a vitamin D deficiency, talk to your doctor about whether a supplement might be right for you. If you're concerned about your vitamin D level, ask your doctor about getting it checked.