Overview

There are no specific tests that can confirm a diagnosis of fibromyalgia. But you may have lab tests to rule out other diseases. Or these tests can find out if you have another disease along with fibromyalgia.

Fibromyalgia may occur along with other joint and muscle (rheumatic) diseases, such as rheumatoid arthritis. Finding these other conditions is important, because they may need different treatment.

If your doctor thinks that you may have another muscle or joint disease based on your symptoms, history, and physical exam, your doctor may do:

• A complete blood count (CBC).
• An erythrocyte sedimentation rate (ESR) or a C-reactive protein (CRP) test. It can help find diseases that cause inflammation, such as polymyalgia rheumatica.
• Thyroid hormone tests to check for low or high thyroid gland activity. Thyroid problems can cause fatigue and muscle soreness.
• A blood calcium level test to check for a low or high calcium level. A low level can cause muscle cramps. A high level may mean you have an overactive parathyroid gland.

The test results may show that you have a disease other than fibromyalgia. Or you might have both fibromyalgia and another condition. Test results can be false-positive.

Doctors don't use these tests to diagnose fibromyalgia. You only need them if your medical history and physical exam suggest that you might have a condition other than fibromyalgia.