Chronic fatigue syndrome (CFS) is a condition that causes severe fatigue that interferes with a person's daily activities. The fatigue is not the result of exertion, and it is not relieved by rest.

The cause of CFS is unknown.

Symptoms of CFS include fatigue, sleep problems, difficulty concentrating and thinking clearly, memory problems, fever, headaches, muscle and joint pain, sore throat, and tender glands in the neck or armpits. Normal activity and light exertion cause tiredness and malaise that usually last longer than 24 hours.

Physical exams and laboratory tests are done to rule out other causes of the symptoms. Because there is no test that can identify CFS, it can be diagnosed only by ruling out all other conditions.

Treatment for CFS is directed at relieving fatigue and other symptoms enough for a person to function normally and gradually return to his or her previous level of activity. Home treatment is a very important part of treating CFS. Diet, exercise, and good sleep habits can often help relieve and control symptoms. Many people with CFS find that their symptoms improve over time, allowing them to return to near normal activity in 1 to 2 years.