People who take oral corticosteroids for arthritis and other illnesses are twice as likely as non-users to have a vitamin D deficiency, according to research from Albert Einstein College of Medicine of Yeshiva University, in New York City. The finding raises the issue of who should be tested for low vitamin D levels and how often.

Corticosteroids, including prednisone, are a class of powerful drugs that reduce inflammation and suppress the immune system. They are prescribed for a wide variety of conditions, including rheumatoid arthritis (RA) and lupus, as well as multiple sclerosis, some types of cancer, asthma and skin rashes – including those caused by poison ivy. They can be prescribed short-term – until a rash clears up or until another drug can take effect, for example – or they may be used long-term. Corticosteroids come in skin creams, injections and inhaled forms; however, this study examined only people who took them orally.

The cross-sectional study, published in The Journal of Clinical Endocrinology and Metabolism, reviewed data from more than 22,500 Americans of all ages. Of those, 181 had used oral corticosteroids in the previous 30 days. Eleven percent of oral corticosteroid users had a “severe” vitamin D deficiency compared with 5 percent of those who hadn’t taken oral corticosteroids in the previous 30 days.

The lead author of the study recommends testing vitamin D levels before and during treatment for patients on oral corticosteroids. “Patients should ask their doctors about their vitamin D levels, especially patients who are on steroids,” says Amy Skversky, MD, an assistant professor of pediatrics at Einstein and Montefiore Medical Center, also in New York. She encourages continuous vitamin D monitoring among long-term users because they may be at an even higher risk of vitamin D deficiency.

The body needs vitamin D to absorb calcium, which is crucial for maintaining strong bones and staving off osteoporosis. Vitamin D, which the body produces when the skin is exposed to sunlight, also is believed to help lower inflammation. There also is evidence that vitamin D protects the body from a host of ailments including diabetes, high blood pressure and some cancers.