Medical Testing for Fibromyalgia


No specific single medical laboratory test for Fibromyalgia exists. A diagnosis of fibromyalgia is difficult to achieve for many individuals for a number of reasons. Fibromyalgia is an extremely individualistic syndrome and no two people experience the same symptoms and progression. Finally, the diagnosis relies heavily on a process of elimination to exclude other conditions that either co-occur with fibromyalgia or mimic it symptomatically.

This article covers a number of conditions that are commonly associated with fibromyalgia, including chronic fatigue syndrome, irritable bowel syndrome, and interstitial cystitis, as well as several that can mimic fibromyalgia, such as Lyme disease, celiac disease, magnesium deficiency, hypothyroidism, and rheumatoid arthritis. Discussions of medical testing related to each and how tests may also relate to Fibromyalgia is noted.  For some patients, these conditions may be diagnosed along with fibromyalgia. For example, in many patients, the symptoms of chronic fatigue syndrome and fibromyalgia overlap to such a great extent that it can be difficult to differentiate one condition from the other. Therefore a single patient may, after careful examination and testing, be diagnosed with both chronic fatigue syndrome and fibromyalgia.

 Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) is difficult to diagnose for a number of reasons. First, like fibromyalgia, there is no diagnostic laboratory test specific to CFS. Second, fatigue and many of the other symptoms found among individuals with CFS are common to many different illnesses. In addition, there are no outward signs of CFS, i.e., individuals with CFS don’t “look sick.” Furthermore, CFS tends to go through cycles of relapse and remission, which can hamper efforts to diagnose based on symptoms. Finally, again like fibromyalgia, the symptoms of CFS tend to vary among individuals, in quantity, type, and severity. Due to these factors, it is estimated that fewer than 20% of the four million Americans with CFS have actually been diagnosed.

A diagnosis of CFS requires persistent or relapsing fatigue for at least six consecutive months, as well as a minimum of four of the following symptoms:

  • Impaired memory or concentration
  • Tender lymph nodes in the neck*
  • Sore throat
  • Muscle pain*
  • Pain in multiple joints that is not arthritis*
  • New-onset (meaning not lifelong) headaches, either tension or migraine*
  • Sleep that is not refreshing*
  • General fatigue, pain, and flu-like symptoms following exercise

The symptoms marked with an * are frequently present in patients with fibromyalgia, illustrating the difficulty in differentiating the diagnosis between fibromyalgia and CFS. Based on certain diagnostic criteria and the exclusion of other potential causes for these symptoms (such as low iron, arthritis, etc.), if an individual has CFS based on these criteria and still meets established diagnostic criteria for fibromyalgia, both CFS and fibromyalgia are generally considered to be co-existing (occurring together) in the same patient.

Depending on the physician, certain tests may also be administered to exclude other causes of fatigue. These include, but are not limited to, the following:

  • routine blood chemistry tests to rule out systemic or auto-immune diseases
  • psychological and/or neuropsychological testing

Interstitial Cystitis

Much like fibromyalgia, there is no test to diagnose interstitial cystitis. In addition, since the symptoms of interstitial cystitis are so similar to other bladder conditions, doctors must rule out other treatable bladder conditions before they are able to diagnose interstitial cystitis. This involves ruling out urinary tract infections and bladder cancer. In women, doctors must also rule out  endometriosis (a condition in which cells that line the uterus grow out into other areas of the body), while for men they must exclude chronic prostate inflammation or chronic pelvic pain syndrome.

The diagnosis of interstitial cystitis in the general population is based on evaluating the following: 1) the presence of pain related to the bladder, also taking into account the frequency and urgency of urination; and 2) the absence of other diseases that could cause the symptoms.

Certain diagnostic tests that can help to exclude other diseases include the following:

  • urinalysis:  physical, chemical, and microscopic analysis of urine
  • urine culture:  a lab test to check for bacteria and other germs in the urine
  • cystoscopy:  a test that allows the doctor to look at the interior lining of the bladder and urethra
  • biopsy (tissue sample) of the bladder wall and urethra

Irritable Bowel Syndrome

Much like interstitial cystitis and chronic fatigue syndrome, the diagnosis of irritable bowel syndrome (IBS) is largely achieved through a process of elimination; however, there are a specific set of diagnostic criteria that physicians can use to aid in the diagnosis. These are known as the Rome criteria, and they require that certain signs and symptoms be present before a doctor can diagnose IBS. According to the Rome criteria, to receive a diagnosis of IBS, patients must have abdominal pain and discomfort lasting at least 12 weeks, however the weeks do not have to occur consecutively. In addition, patients must also have at least two of the following:

  • change in frequency or consistency of their stool
  • straining, urgency, or a feeling that they cannot empty their bowels
  • mucus in the stool
  • bloating or abdominal distension

“Red flag” signs and symptoms that may prompt a physician to employ further testing including:

  • onset after the age of 50
  • weight loss
  • rectal bleeding
  • fever
  • nausea or recurrent vomiting
  • abdominal pain that is not completely relieved by a bowel movement
  • diarrhea that is persistent or awakens patients from sleep

In addition, some physicians may recommend several other tests to check for infection or problems with mal-absorption. Tests that can be used to rule out other causes of the symptoms listed above include the following:

  • flexible sigmoidoscopy:  a test that examines the lower part of the colon with a flexible, lighted tube
  • colonoscopy:  a test in which a small, flexible tube is used to examine the entire length of the colon
  • computerized tomography (CT) scan:  a test that produces a cross-sectional computerized X-ray image of internal organs
  • lactose intolerance testing:  Individuals who do not produce the enzyme lactase are unable to digest the sugar known as lactose, which is commonly found in dairy products. This condition is known as lactose intolerance, and it produces symptoms similar to those caused by IBS. Lactose intolerance tests can help to exclude the presence of this condition.
  • Blood tests to rule out Celiac disease (see below)

 Celiac Disease

Celiac disease is a condition in which the lining of the small intestine becomes damaged, preventing it from absorbing nutrients in food. The damage results from eating gluten, which is a protein found in wheat, barley, rye, and oat-containing products. Fortunately, celiac disease can generally be diagnosed by using a special blood test, as well as by examining a biopsy of the small intestine for microscopic changes that are characteristic of the condition.

Blood tests can be used to detect exceptionally high levels of certain antibodies that recognize gluten as a foreign invader in the body. Antibodies are proteins in the immune system that work to eliminate foreign substances. If celiac disease is suspected, a physician may want to view a small portion of the intestinal tissue under a microscope to check for microscopic damage that is characteristic of the disease. This can be done by inserting a thin, flexible tube known as an endoscope through the mouth, esophagus, and stomach into the small intestine.

Lyme Disease

Lyme disease is a bacterial infection that is transmitted by the bite of infected blacklegged ticks. Both laboratory testing and a detailed history of possible exposures to infected ticks can result in an effective diagnosis of Lyme disease.

 Blood tests to detect Lyme disease measure antibodies that the body makes in response to the infection; however, it can take several weeks following contraction of the infection for the body to produce enough antibodies to show up on a blood test. As a result, individuals who have Lyme disease but who are tested in the first few weeks of their illness will frequently test negative for Lyme disease. For those who have had the disease longer than four to six weeks, blood tests will almost universally be positive. Along the same lines, individuals who have been ill for months or years and who have negative blood test results will almost always not have Lyme disease.

Magnesium Deficiency

Magnesium is a mineral that is essential to the functioning of almost every organ in the body, and is particularly important to the transmission of the nerve signals that cause muscles to contract and relax. If magnesium deficiency is suspected, a simple blood test can be used to measure the amount of magnesium in the blood. Normal value ranges differ slightly between laboratories, however in general, normal blood levels of magnesium range from 1.7 to 2.2 mg/dL (milligrams per deciliter). If an individual’s blood test shows that their magnesium level is below 1.7 mg/dL, their physician may recommend that they take an oral magnesium supplement until their magnesium level returns to normal.


Hypothyroidism is a disorder of the thyroid gland in which the gland does not produce sufficient levels of thyroid hormone. The diagnosis of hypothyroidism is generally based on symptoms as well as on the results of blood tests that are designed to measure a hormone known as TSH, or thyroid stimulating hormone. In addition, sometimes the hormone thyroxine will also be measured. Low levels of thyroxine and high levels of TSH are indicative of hypothyroidism.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory disorder that involves the small joints in the hands and feet. In contrast to arthritis, which results in constant wear and tear on joints due to inflammation, RA affects the lining of joints and causes extremely painful swelling. Eventually, this swelling can result in the erosion of bone as well as joint deformities. RA is considered to be an autoimmune disorder, in which the body’s immune system mistakenly attacks the body’s own tissues. The diagnosis of RA can initially be difficult, as the signs and symptoms of RA often mimic those of other diseases. Like fibromyalgia, there is no one test that can specifically detect the presence of RA. Physical examinations can be used to assess joints for swelling, redness, and warmth. Blood tests can also be useful. Individuals with RA usually have an elevated erythrocyte sedimentation rate, or ESR (also referred to as “sed rate”). ESR is indicative of an inflammatory process in the body, and can help narrow the focus of diagnosis. Other blood tests can be used to look for the presence of rheumatoid factor antibodies and anti-cyclic citrullinated peptide (anti-CCP) antibodies.

Learn More

You can learn more about the history of Fibromyalgia diagnosis HERE and about the current standard for fibromyalgia diagnosis HERE including information on current non-laboratory testing criteria.




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3.        Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, Tugwell P, Campbell SM, Abeles M, Clark P, et al. The American College of Rheumatology 1990 criteria for the classification of fibromyalgia. Report of the Multicenter Criteria Committee. Arthritis Rheum. 1990;33(2):160-172.

4.      Wolfe F, Hauser W. Fibromyalgia diagnosis and diagnostic criteria. Ann Med. 2011;43(7):495-502.

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