If you have chronic pain, get your blood levels of vitamin D checked. New research has found that one in four people who suffer from chronic pain have inadequate blood levels of vitamin D, which may be contributing to their pain problems.

Researchers have known that  low vitamin D can cause pain and muscle weakness, according to the study’s lead author, W. Michael Hooten, M.D., medical director of the Mayo Comprehensive Pain Rehabilitation Center, in Rochester, Minnesota. It’s also known that pain that is a result of vitamin D deficiency responds poorly to pain medications. In this study, people with low blood levels of vitamin D needed higher doses of morphine, for a longer period of time, than those with adequate levels. They also reported lower levels of physical functioning and had a poorer view of their overall health.

Vitamin D inadequacy is more common than previously thought, and has been found in people with fibromyalgia, chronic fatigue syndrome, depression, osteoarthritis, rheumatoid arthritis and multiple sclerosis. Treatment is easy and inexpensive and has essentially no side effects, Dr. Hooten says. Your blood serum should be tested for 25-hydroxyvitamin D, and the level should be at least 30 ng/ml to be adequate. You may need to take large amounts of vitamin D initially, under medical supervision, to get your blood levels up. Once you’ve reached a good range, a smaller dose, 800-1,000 IU a day, may keep you at an optimal level.

Many medical conditions can contribute to low vitamin D, including malabsorption, chronic kidney disease, hyperthyroidism, parathyroid problems and some types of cancer (granuloma or lymphoma). Use of steroid drugs can also deplete vitamin D. A vitamin D check-up may help ward off future problems as well as treat existing conditions.