Chronic Fatigue: Symptom vs. Disease

Woman with chronic fatigue at work
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The terms "chronic fatigue" and "chronic fatigue syndrome" often are used interchangeably, but they're actually two very different things:

  1. Chronic fatigue is a symptom of just about every illness and a consequence of lifestyle choices and factors, such as not getting adequate rest or being extremely busy. It just means that you're tired all the time.
  2. Chronic fatigue syndrome is a disease with specific diagnostic criteria and a lengthy symptoms list that includes fatigue that's not relieved by rest, exercise intolerance (post-exertional malaise), flu-like symptoms, and cognitive dysfunction.

    When you're trying to learn about your illness and find treatments for it, it pays to make sure you're looking at information about the disease and not the symptom.

    Understanding Fatigue

    Fatigue is one of the most common complaints doctors hear. Much of the time it's caused by stress, lack of sleep, overexertion, or minor illness, such as a cold. Typically, fatigue goes away when you get rest or recover from being sick.

    In both chronic fatigue and ME/CFS, fatigue is extreme and constant. It makes it difficult or impossible for you to function at even the most basic level. Think of the way you felt the last time you were seriously ill, severely sleep deprived, or coming out from under anesthesia — that's the kind of fatigue we're talking about.

    What Is Chronic Fatigue (the Symptom)?

    If you simply have chronic fatigue, it means that you have exhaustion or lack of energy for six months or longer.

    Chronic fatigue is generally a symptom of something else, such as:

    • High stress levels
    • Nutritional deficiency

    Some causes of chronic fatigue (such as lack of sleep, nutritional deficiency, or short-term infection) have an obvious solution and are somewhat easy to correct. When caused by a chronic illness, chronic fatigue can be treated but not cured.

    In some cases, doctors can't figure out the cause of chronic fatigue, but the person doesn't meet the diagnostic criteria for ME/CFS. Those cases are diagnosed as idopathic chronic fatigue. (Idiopathic means without known cause.)

    Chronic Fatigue Syndrome

    To get a diagnosis of chronic fatigue syndrome, you need more than extreme, persistent fatigue that lasts longer than six months. You've also got to have at least four of the following, also for longer than six months but starting after the fatigue:

    • Impaired memory or concentration
    • Post-exertional malaise
    • Unrefreshing sleep
    • Muscle pain
    • Joint pain without swelling or redness
    • Headaches of a new type or severity
    • Sore throat that's frequent or recurring
    • Tender cervical or axillary lymph nodes

    In addition to these diagnostic criteria, ME/CFS has about 50 recognized symptoms, including dizziness and balance problems, allergies and chemical sensitivities, anxiety, stiffness, numbness, and irregular heart beat.

    While not required for a diagnosis, these other symptoms can help your doctor identify what's going on in your body.

    Why Does it Matter?

    It's in your best interest to pay attention to whether websites and other information sources are talking about the symptom or the disease. It might seem like they're just using a shorter form of a long name and are really talking about the same thing.

    Sometimes, that may be true. However, other times, it may be used to deceive you. Say a website claims that a certain product is proven to "relieve chronic fatigue." Which one are they really talking about? If they're talking about the symptom, that product is unlikely to be much help for ME/CFS.

    The language might be used intentionally to make you think it could work for you.

    People who are educated about ME/CFS know to use the proper abbreviations, whether that's CFS, ME/CFS, CFS/ME, CFIDS, or SEID. Dropping the "syndrome" out of the name is frowned on in the patient/advocate/research community because it's inaccurate. When it comes to your health, you can't afford to fall for deception or listen to inaccurate sources.


    June 2003 National Institutes of Health. "Chronic Fatigue Research: Challenges and Opportunities."

    2007 University of Maryland Medical Center (UMMC). All rights reserved. "Chronic Fatigue Syndrome"

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