This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

Clinical features

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Suspect ME/CFS if:

  • the person has had all of the persistent symptoms * for a minimum of 6 weeks in adults and 4 weeks in children and young people and
  • the person's ability to engage in occupational, educational, social or personal activities is significantly reduced from pre-illness levels and
  • symptoms are not explained by another condition

*Persistent symptoms in suspected ME/CFS

All of these symptoms should be present:

  • debilitating fatigue that is worsened by activity, is not caused by excessive cognitive, physical, emotional or social exertion, and is not significantly relieved by rest.
  • post-exertional malaise after activity in which the worsening of symptoms:
    • is often delayed in onset by hours or days
    • is disproportionate to the activity
    • as a prolonged recovery time that may last hours, days, weeks or longer

  • unrefreshing sleep or sleep disturbance (or both), which may include:
    • feeling exhausted, feeling flu-like and stiff on waking
    • broken or shallow sleep, altered sleep pattern or hypersomnia

  • cognitive difficulties (sometimes described as 'brain fog'), which may include problems finding words or numbers, difficulty in speaking, slowed responsiveness, short-term memory problems, and difficulty concentrating or multitasking.


  • post-exertional malaise
    • worsening of symptoms that can follow minimal cognitive, physical, emotional or social activity, or activity that could previously be tolerated. Symptoms can typically worsen 12 to 48 hours after activity and last for days or even weeks, sometimes leading to a relapse. Post-exertional malaise may also be referred to as post-exertional symptom exacerbation
  • fatigue in ME/CFS typically has the following components:
    • feeling flu-like, especially in the early days of the illness
    • restlessness or feeling 'wired but tired'
    • low energy or a lack of physical energy to start or finish activities of daily living and the sensation of being 'physically drained'
    • cognitive fatigue that worsens existing difficulties
    • rapid loss of muscle strength or stamina after starting an activity, causing for example, sudden weakness, clumsiness, lack of coordination, and being unable to repeat physical effort consistently

Diagnose ME (myalgic encephalitis)/CFS (chronic fatigue syndrome) in a child, young person or adult who has the symptoms as above that have persisted for 3 months and are not explained by another condition


  • clinical features that can be caused by other serious conditions ('red flags') should not be attributed to CFS/ME without consideration of alternative diagnoses or comorbidities. In particular, the following features should be investigated:
    • localising/focal neurological signs
    • clinical features of inflammatory arthritis or connective tissue disease
    • clinical features of cardiorespiratory disease
    • significant weight loss
    • sleep apnoea
    • clinically significant lymphadenopathy


  1. Prescribers' Journal (2000), 40 (2), 99-106.
  2. NICE (October 2021). Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management

Create an account to add page annotations

Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.