I was diagnosed by a rheumatologist as having fibromyalgia, my gp thinks it is either lupus or ms. how will they actually make a diagnosis?

See below: There are no specific tests for fibromyalgia which is a condition in which there is widespread pain above and below the waist and on both sides of the body. Ms and lupus both have certain lab tests as well as other tests that can establish either of those diagnoses.

No diagnosis yet: MS can be diagnosed with the right history and exam, or if needed, MRI and spinal tap test results. SLE can be diagnosed sometimes with the help of blood tests. FM is not diagnosed by abnormal MRI, spinal tap or blood tests- that is a big difference. Perhaps your doc will do the easy tests first, or get some other specialist physicians involved to think about the case.