Persistent Fatigue
The common medical causes of ongoing tiredness, the blood tests usually done, and when it needs urgent assessment.
Last revised
Tiredness that does not improve with rest, lasting weeks, is a symptom rather than a lifestyle state. It has a long list of causes, many of them simple to test for and treat.
The usual first tests
A GP assessing persistent fatigue will typically arrange a full blood count for anaemia, ferritin for iron stores, thyroid function, HbA1c or glucose for diabetes, kidney and liver function, calcium, and inflammatory markers. Coeliac serology and vitamin D are commonly added. This panel covers a large share of the treatable causes and is worth asking for specifically.
Sleep disorders are commonly missed
Obstructive sleep apnoea produces fatigue that no amount of time in bed corrects, and is substantially underdiagnosed, particularly in women. Ask whoever sleeps near you about snoring and breathing pauses. Restless legs, chronic insomnia and shift work all produce the same complaint through different mechanisms.
Mental health and medication
Depression and anxiety frequently present as fatigue rather than as low mood, particularly in men and in older adults. Many common medicines cause tiredness, including beta blockers, some antihistamines, opioids, antidepressants and statins in a minority. A medication review is a reasonable early step.
When fatigue is the main story
Where fatigue is disabling, lasts more than three months, and worsens disproportionately after activity — post-exertional malaise — myalgic encephalomyelitis/chronic fatigue syndrome should be considered. NICE guidance was substantially revised in 2021 and no longer recommends graded exercise therapy as a treatment. Long COVID produces an overlapping picture and has its own referral pathways.
At a glance
| Term | Detail |
|---|---|
| Usual blood panel | FBC, ferritin, thyroid, HbA1c, kidney, liver, calcium, inflammatory markers |
| Commonly added | coeliac serology, vitamin D |
| Frequently missed cause | obstructive sleep apnoea |
| Threshold for ME/CFS consideration | disabling fatigue over 3 months with post-exertional malaise |
| Graded exercise therapy for ME/CFS | no longer recommended by NICE since 2021 |
| Common drug causes | beta blockers, antihistamines, opioids, antidepressants |
When to get help
See a GP promptly for fatigue with unexplained weight loss, night sweats, persistent fever, swollen glands, unusual bruising or bleeding, or breathlessness at rest. Seek urgent assessment for fatigue with chest pain, fainting, or new confusion. Do not drive if you are fighting to stay awake.
Where to go next
Where this comes from
- NICE - Tiredness/fatigue in adults clinical knowledge summary
- NICE - Myalgic encephalomyelitis/chronic fatigue syndrome: diagnosis and management
- NHS - Self-help tips to fight tiredness
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.
