by EBSCO Medical Review Board

Chronic fatigue syndrome (CFS) is a long term and complex disease. It causes extreme tiredness. This makes it hard to do daily activities, work, or go to school. Rest does not make the tiredness better. CFS is sometimes known as systemic exertion intolerance disease (SEID). It is also called myalgic encephalomyelitis.

Problems may exist for many months to years. Symptoms may vary in severity. Some people get better over time, while others continue to get worse. Most will have a cycle of improvement and flare ups.

CFS is very hard to diagnose. It may take some time before a diagnosis of CFS is made. The cause of CFS is not known. The most common theory is that CFS is set off by an infection or other immune system problems.

What are the risk factors for chronic fatigue syndrome?What are the symptoms of chronic fatigue syndrome?How is chronic fatigue syndrome diagnosed?What are the treatments for chronic fatigue syndrome?Are there screening tests for chronic fatigue syndrome?How can I reduce my risk of chronic fatigue syndrome?What questions should I ask my doctor?Where can I get more information about chronic fatigue syndrome?


Chronic fatigue syndrome. EBSCO DynaMed website. Available at: Accessed April 12, 2022.

Chronic fatigue syndrome. Merck Manual Professional Version website. Available at: Accessed April 12, 2022.

Treatment of ME/CFS. Centers for Disease Control and Prevention website. Available at: Accessed April 12, 2022.

Yancey JR. Thomas SM. Chronic fatigue syndrome: diagnosis and treatment. Am Fam Physician. 2012;8(68):741-746.

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