It is done by ruling out everything else. In my years of searching for a diagnosis I had many CT scans and MRI's. Then I had brain wave tests done and mental testing, and was referred to mental health therapists for treatment of depression. I saw 12 different neurologists, as well as, physicians in the fields of urology and gynecology, allergy testing and cardiology. Finally someone referred me to a mayo clinic rheumatologist and I recieved my first diagnosis of Fibromyalgia. One would hope that was the end of searching for answers and having a doctor to help handle the pain and related problems, but that was not the case. Even the doctor who diagnosised it, said he did not believe in it and told me now go home and just live with it, and I was unable to get appointments with him again. Years later, many doctors later, I was re-diagnosised. Other than medications most of the symptoms will be handled by your family doctor or other physicians in different fields of medicine who for the most part have your best interests at heart.