Overview
Chronic Fatigue Syndrome (CFS), also called Myalgic Encephalomyelitis (ME), is a complex, long-term condition characterised by extreme fatigue that is not explained by other conditions and does not improve with rest. Even minor physical or mental exertion can cause a worsening of symptoms (post-exertional malaise) that can last days.
How common is it?
ME/CFS affects approximately 250,000 people in the UK. It affects people of all ages but is more common in women and tends to peak in the 40s.
Causes and risk factors
The exact cause is unknown but ME/CFS often begins after a viral infection. Research points to abnormalities in immune function, energy production in cells, and the autonomic nervous system.
Common risk factors
- Viral infection (often appears after glandular fever, COVID-19)
- Female sex
- Previous mental health conditions
- Stressful life events preceding onset
- Possible genetic susceptibility
- Dysfunction of immune and mitochondrial systems
Symptoms
- Severe fatigue not relieved by sleep or rest
- Post-exertional malaise: worsening after even mild activity
- Unrefreshing sleep
- Cognitive difficulties: poor memory, concentration ('brain fog')
- Muscle and joint pain
- Headaches
- Sore throat and enlarged lymph nodes
- Dizziness when standing (orthostatic intolerance)
When to see a doctor
See a doctor if you have persistent, unexplained fatigue lasting more than 4 weeks that significantly limits your daily activities. Blood tests are needed to rule out treatable causes such as anaemia or thyroid disease.
Diagnosis
Diagnosis is clinical, based on specific criteria (the Canadian Consensus Criteria or NICE 2021 guidelines) after excluding other causes. Blood tests, thyroid function, and sleep assessment are part of the workup.
Treatments
Pacing and energy management
Keeping activity within an individual's current energy envelope to avoid post-exertional malaise. Planned rest breaks and gradual, cautious increases over time.
Sleep management
Establishing regular sleep patterns and treating sleep disorders (if present) can reduce fatigue severity.
Symptom management
Pain relief, low-dose antidepressants for sleep disturbance and pain, antihistamines, and medication for orthostatic symptoms as needed.
Self-care and lifestyle
- Keep an activity diary to identify your energy limits and patterns
- Prioritise the most important activities when energy is lowest
- Rest proactively, before fatigue hits, not only in response to it
- Connect with ME/CFS support organisations for practical guidance
Prevention
There is no proven way to prevent ME/CFS. After a viral infection, pacing activity during recovery and avoiding pushing through extreme fatigue may be protective.