Overview
Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), is a complex, long-term illness characterised by extreme fatigue that is not improved by rest and is worsened by physical or mental activity. The cause remains poorly understood, though it often follows a viral infection. CFS/ME affects all age groups and can be profoundly disabling, with many people unable to work or carry out daily activities.
Causes and risk factors
The following factors are associated with the development of Chronic Fatigue Syndrome (CFS/ME):
- Often triggered by viral infection (post-viral syndrome)
- Immune system dysfunction
- Nervous system abnormalities
- Hormonal imbalances
- Genetic predisposition
- Psychological and physical stress
- Associated with COVID-19 (Long COVID)
Signs and symptoms
Common signs and symptoms of Chronic Fatigue Syndrome (CFS/ME) include:
- Extreme fatigue unrelieved by rest
- Post-exertional malaise — worsening after activity
- Cognitive difficulties ('brain fog')
- Unrefreshing sleep
- Muscle and joint pain without swelling
- Headaches
- Sore throat and tender lymph nodes
- Dizziness when standing (orthostatic intolerance)
- Sensitivity to light, sound, and temperature
Diagnosis
Chronic Fatigue Syndrome (CFS/ME) is typically diagnosed through a combination of medical history, physical examination, and appropriate investigations such as blood tests, imaging, or specialist review, depending on the specific condition and presentation. Your doctor will consider all relevant symptoms and risk factors before making a diagnosis.
Treatment options
Treatment approaches for Chronic Fatigue Syndrome (CFS/ME) may include:
- Pacing — managing activity to stay within energy limits
- Cognitive behavioural therapy (CBT) for some patients
- Graded exercise therapy remains controversial
- Sleep management strategies
- Pain relief medications
- Treating co-existing conditions
- Dietary interventions
- Specialist ME/CFS clinics
Prevention
No known prevention. Resting adequately after viral infections and avoiding pushing through fatigue may reduce risk of developing CFS.
Complications
If left untreated or poorly managed, Chronic Fatigue Syndrome (CFS/ME) can lead to complications including:
Severe disability, social isolation, depression, and anxiety. Many people cannot work for months or years.
Sources and references: This article is written in accordance with NHS UK, WHO, and Mayo Clinic clinical guidelines. It is reviewed for accuracy by the SymptomSense content team. ICD-10 code: G93.3. Last reviewed June 2026.