Diagnosis of Chronic Fatigue Syndrome (CFS)

A diagnosis of chronic fatigue syndrome (CFS) is based on the following criteria:

  • Severe, chronic fatigue that lasts for at least 6 months in 50% of time and is not due to another illness or medical cause
  • At least four of the following eight symptoms:
    • Impairment of short-term memory or concentration
    • Sore throat
    • Tender lymph nodes
    • Muscle pain
    • Joint pain without swelling or redness
    • Headaches
    • Sleep that is not refreshing
    • Prolonged fatigue lasting 24 hours or more after exercise

If your symptoms match these criteria, your healthcare provider should further investigate the possibility that you may have CFS. The diagnostic process typically includes the following:

Medical evaluation—Your healthcare provider will obtain a detailed medical history and perform a complete physical exam.

Standardized laboratory tests—You will receive a standard series of tests to analyze your blood and urine. This should help your healthcare provider identify other possible causes of illness. If test results suggest an alternative explanation for your symptoms, additional tests may be performed to confirm that possibility. If no cause for the symptoms is identified, your healthcare provider may render a diagnosis of CFS by exclusion of the other conditions and if the case definition is met.

The number and type of tests performed may vary depending on your history. The following tests are often used to exclude other causes of fatiguing illness:

  • Alanine aminotransferase (ALT) (liver test)
  • Albumin (liver test)
  • Alkaline phosphatase (ALP) (bone and liver test)
  • Blood urea nitrogen (BUN) (kidney test)
  • Calcium
  • Complete blood count (white and red cells)
  • Creatinine (kidney test)
  • Electrolytes (salt and potassium)
  • Erythrocyte sedimentation rate (ESR) (inflammation test)
  • Globulin (liver test)
  • Glucose (blood sugar)
  • Phosphorus
  • Thyroid stimulating hormone (TSH)
  • Total protein
  • Transferrin saturation (iron level)
  • Urinalysis

Further testing may be required to confirm a diagnosis for illness other than CFS. For example:

Psychological/neurological tests—Your healthcare provider may want to assess the impact of fatiguing illness on certain cognitive or reasoning skills, such as your concentration, memory, and organization. You may also be given a personality assessment. This may assist in determining your coping abilities and whether you have a coexisting affective disorder like depression, panic disorder, or other anxiety disorders that need to be treated.


Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ .

Craig T, Kakumanu S. Chronic fatigue syndrome: evaluation and treatment. Am Fam Physician. 2002;65:1083-1090.

Devanur LD, Kerr JR. Chronic fatigue syndrome. J Clin Virol. 2006;37:139-150.

National Institute of Allergy and Infectious Diseases website. Available at: http://www3.niaid.nih.gov/ .

Prins JB, van der Meer JW, Bleijenberg G. Chronic fatigue syndrome. Lancet. 2006;367:346-355.

Last reviewed April 2007 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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