Fatigue in Long-Term Illness
Persistent tiredness that is part of a condition rather than a lack of sleep.
Last revised
Key takeaways
- Treatable contributors: anaemia, thyroid disease, depression, sleep apnoea, medication
- Usual first tests: FBC, ferritin, thyroid, HbA1c, kidney, liver, calcium, inflammatory markers
- Most useful single change: Ask for the standard blood panel rather than accepting it as inevitable.
- Commonest mistake: Assuming fatigue is simply part of the condition without investigation.
- See a doctor if any of the signs under "When to get help" below apply to you.
Why it matters
It is among the most disabling symptoms reported and among the least investigated, and some causes are entirely treatable.
The numbers, in one place
| Measure | Figure |
|---|---|
| Treatable contributors | anaemia, thyroid disease, depression, sleep apnoea, medication |
| Usual first tests | FBC, ferritin, thyroid, HbA1c, kidney, liver, calcium, inflammatory markers |
| Graded activity | helps in several conditions; pacing in others |
| Deconditioning | both a cause and a consequence |
What helps
- Ask for the standard blood panel rather than accepting it as inevitable
- Ask whether any of your medicines contribute
- Pace activity rather than alternating between overdoing it and crashing
What to avoid
- Assuming fatigue is simply part of the condition without investigation
- Complete rest, which deconditions further
Where to go next
- What People Get Wrong About Fatigue in Long-Term Illness
- Fatigue in Long-Term Illness: A Beginner-Friendly Start
- What the Guidance Really Says About Mental Health and Long-Term Illness
- What the Guidance Really Says About Sick Day Rules
When to get help
See a GP for fatigue with unexplained weight loss, night sweats, persistent fever, swollen glands, unusual bruising, or breathlessness at rest. Seek urgent assessment for fatigue with chest pain or fainting. Do not drive if you are fighting to stay awake.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.