Persistent Fatigue
The common medical causes of ongoing tiredness, the blood tests usually done, and when it needs urgent care.
Last revised
Tiredness that does not improve with rest and lasts 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 doctor assessing persistent fatigue will often order a complete blood count for anemia, ferritin for iron stores, thyroid tests, A1C or glucose for diabetes, a metabolic panel covering kidney and liver function and calcium, and sometimes inflammatory markers. Celiac disease testing and vitamin levels may be added depending on symptoms. This covers a large share of the treatable causes and is worth asking about specifically.
Sleep disorders are commonly missed
Obstructive sleep apnea causes fatigue that no amount of time in bed fixes, and it is substantially underdiagnosed, particularly in women. Ask whoever sleeps near you about snoring and pauses in breathing. Restless legs, chronic insomnia and shift work all produce the same complaint through different mechanisms.
Mental health and medication
Depression and anxiety frequently show up as fatigue rather than low mood, particularly in men and older adults. Many common medicines cause tiredness, including beta blockers, some antihistamines, opioids, antidepressants and, in a minority of people, statins. A medication review with your doctor or pharmacist is a reasonable early step.
When fatigue is the main story
Where fatigue is disabling, lasts six months or more, and gets disproportionately worse after activity, known as post-exertional malaise, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) should be considered. CDC guidance emphasizes pacing activity to avoid crashes, and graded exercise therapy is no longer recommended. Long COVID can cause a similar, overlapping picture.
At a glance
| Term | Detail |
|---|---|
| Usual blood tests | CBC, ferritin, thyroid, A1C, metabolic panel, sometimes inflammatory markers |
| Sometimes added | celiac disease testing, vitamin levels |
| Frequently missed cause | obstructive sleep apnea |
| When to consider ME/CFS | disabling fatigue for 6 months or more with post-exertional malaise |
| Graded exercise therapy for ME/CFS | no longer recommended; CDC emphasizes pacing |
| Common medicine causes | beta blockers, antihistamines, opioids, antidepressants |
When to get help
See your doctor promptly for fatigue with unexplained weight loss, night sweats, persistent fever, swollen glands, unusual bruising or bleeding, or shortness of breath at rest. Call 911 for fatigue with chest pain, fainting, or sudden confusion. If you have thoughts of harming yourself, call or text 988. Do not drive if you are fighting to stay awake.
Where this comes from
- MedlinePlus - Fatigue
- CDC - Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
- National Heart, Lung, and Blood Institute - Sleep Apnea
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, 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 911.
