In brief: “Fatigue” describes marked exhaustion but is not one single diagnosis. Causes can include sleep problems, stress, medicines, anaemia, thyroid disease, infections and ME/CFS.
Possible causes
| Area | Examples |
|---|---|
| Sleep | Insomnia, sleep apnoea |
| Metabolic | Anaemia, diabetes, thyroid disease |
| Psychological | Depression, anxiety, chronic stress |
| Medicines/illness | Many drugs, infections, chronic disease |
NHS advises medical assessment when tiredness lasts for weeks, affects daily life or comes with other symptoms.[1]
ME/CFS is not simply severe tiredness
ME/CFS is a distinct condition. Core features include marked fatigue, unrefreshing sleep, cognitive problems and worsening after physical or mental activity—post-exertional malaise (PEM).[2]
Manage activity individually
Physical activity often helps general tiredness, but fixed incremental exercise programmes are not appropriate for ME/CFS. Energy and activity management should be symptom-guided.
Assessment
History, examination and tests such as blood count, thyroid or metabolic studies may be appropriate depending on symptoms.
FAQ
Is fatigue the same as normal tiredness?
Not always.
Is all chronic fatigue ME/CFS?
No.
What is PEM?
A delayed and significant worsening of symptoms after physical or mental exertion.
When should someone see a doctor?
When exhaustion persists for weeks, limits daily life or comes with warning signs.
Conclusion
Fatigue is a symptom with many possible causes. Good care starts with assessment and a strategy matched to the actual cause.
