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Diagnosis of Chronic Fatigue Syndrome (CFS)

  • Amy Scholten, MPH
Publication Type:

Condition InDepth

Diagnosis of Chronic Fatigue Syndrome (CFS)

CFS can be hard to diagnose. It may take some time. There are many conditions that cause similar symptoms.

The doctor will ask about symptoms, past health, and family health history. There are no standard tests for CFS. But, tests may be done to rule out other issues. People with CFS often have normal physical exams and test results.

If tests are normal, the doctor may suspect CFS.

Diagnosis may be based on 3 of the following symptoms:

  • 6 or more months of severe tiredness—with reduced or impaired functioning that:
    • Affects daily activities, such as work and relationships
    • Does not get better with good sleep
    • Is not due to too much activity
  • Severe tiredness or muscle fatigue after activity—at least 50% of the time
  • Sleep problems at least 50% of the time—moderate to severe

One or both of these symptoms:

  • Problems with memory, focus, or thinking at least 50% of the time—moderate to severe
  • Lightheadedness or eyesight problems when standing or sitting up

Tests will be based on past health, a physical exam, and symptoms. Not everyone will have all tests. Tests may include:


  • Chronic fatigue syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/chronic-fatigue-syndrome.
  • Chronic fatigue syndrome. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/special-subjects/chronic-fatigue-syndrome/chronic-fatigue-syndrome.
  • Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, Board on the Health of Select Populations, Institute of Medicine. Beyond myalgic encephalomyelitis/chronic fatigue syndrome: redefining an illness. Washington (DC): National Academies Press (US); 2015 Feb 10. Available at: https://www.ncbi.nlm.nih.gov/books/NBK274235.
  • Diagnosis of ME/CFS. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/me-cfs/symptoms-diagnosis/diagnosis.html.


  • Marcin Chwistek, MD
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.