There's no test for Chronic Fatigue Syndrome (CFS), but there are clear guidelines to help doctors diagnose the condition.
It can take a long time for CFS to be diagnosed, as other conditions that cause similar symptoms need to be ruled out first.
You may be given some advice about managing your symptoms before a diagnosis is confirmed.
If you see your GP about persistent and excessive fatigue, they'll ask you about your medical history and may carry out a physical examination.
Guidelines released in 2007 from the National Institute for Health and Care Excellence (NICE) state doctors should consider diagnosing CFS if a person has fatigue and all of the following apply:
The person should also have one or more of these symptoms:
This diagnosis should be confirmed by a clinician after other conditions have been ruled out. The symptoms listed above must have persisted for at least four months in an adult and three months in a child or young person.