The short answer
A cough that lingers is usually caused by a viral infection, post-nasal drip, asthma, acid reflux, or smoking — not lung cancer. A cough is more worth checking when it lasts more than about three weeks, changes, or comes with coughing up blood, chest discomfort, or breathlessness.
Most lasting coughs come from infections, allergies, asthma, or reflux — not cancer.
A cough lasting more than about three weeks is worth checking.
Coughing up blood should always be checked promptly.
Risk is higher for people who smoke or used to smoke.
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The full explanation.
The simple version
Coughs are extremely common and usually clear on their own. A cough that lingers after a cold, or one from allergies, asthma, or reflux, is far more likely than lung cancer. Still, a cough that will not go away is worth checking, especially for people who smoke.
What usually causes a lasting cough
Common causes include a lingering viral infection, post-nasal drip from allergies or sinus problems, asthma, acid reflux, smoking, and some blood-pressure medicines. These can keep a cough going for weeks but are not cancer.
When a cough is more worth checking
A cough is more worth a doctor's look when it lasts more than about three weeks, changes in character, or comes with coughing up blood, chest discomfort, breathlessness, hoarseness, or unexplained weight loss. Coughing up blood should always be checked promptly.
When to see a doctor
See a doctor for a cough that lasts more than about three weeks, keeps worsening, or comes with coughing up blood or breathlessness. People who smoke or used to smoke should have a lasting cough checked, and can ask about lung cancer screening.
Words to know
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Common questions
▸Does a lasting cough mean lung cancer?
Usually not. Most lingering coughs come from infections, allergies, asthma, or reflux. A cough lasting more than about three weeks is worth checking, though.
▸When should a cough be checked?
See a doctor for a cough that lasts more than about three weeks, changes, or comes with coughing up blood, chest discomfort, or breathlessness.
▸I smoke — should I be more careful?
Yes. People who smoke or used to smoke are at higher risk and should have a lasting cough checked, and can ask about lung cancer screening.
▸What should I do about coughing up blood?
Coughing up blood should always be checked promptly, even though it often has causes other than cancer.
Questions to ask your doctor
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