The short answer
Fatigue that does not improve with rest can be a sign of some cancers, such as leukemia, or of cancers that cause blood loss. It has many causes, but ongoing, unexplained fatigue should be checked.
Cancer-related fatigue is tiredness that does not get better with rest.
It can be an early sign of some cancers, including leukemia.
Cancers that cause slow blood loss, like colon or stomach cancer, can cause fatigue through anemia.
Fatigue has many non-cancer causes, from poor sleep to thyroid problems.
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The full explanation.
The simple version
Everyone feels tired sometimes. But fatigue that does not get better with rest — the kind that lingers and interferes with daily life — can be a sign of some illnesses, including certain cancers. It is worth checking if it lasts or has no clear cause.
Why cancer can cause fatigue
Some cancers, such as leukemia, can cause fatigue early on. Cancers that cause slow, hidden blood loss — like colon or stomach cancer — can lead to anemia, which makes people feel tired and short of breath.
Cancer-related fatigue is tiredness that rest does not fix.
Other causes
Fatigue is very common and usually not cancer. Poor sleep, stress, depression, thyroid problems, infections, and many other conditions cause it. Because the causes overlap, a doctor's evaluation helps find the reason.
When to see a doctor
See a doctor if you feel very tired for no clear reason, if rest does not help, or if the fatigue lasts several weeks or comes with other symptoms such as weight loss or unusual bleeding.
Words to know
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Common questions
▸How is cancer fatigue different from normal tiredness?
Everyday tiredness usually improves with rest. Fatigue that could signal illness is ongoing, is not fixed by rest or sleep, and can interfere with daily life.
▸Which cancers cause fatigue?
Fatigue can be an early sign of some cancers such as leukemia. Cancers that cause slow blood loss, like colon or stomach cancer, can also cause fatigue by leading to anemia.
▸What else causes fatigue?
Many things — poor sleep, stress, depression, anemia, thyroid problems, infections, and other illnesses. A doctor can help sort out the cause.
▸When should I see a doctor?
See a doctor if you feel very tired for no clear reason, if rest does not help, or if fatigue lasts several weeks or comes with other symptoms.
Questions to ask your doctor
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