Why does lung cancer cause coughing up blood?

A tumour in or near an airway can inflame its lining, ulcerate, or interfere with small blood vessels. Blood can then mix with phlegm and come out during a cough. Coughing Up Blood is a common presentation of Lung Cancer, but infection, airway inflammation, blood-thinning medicines, and other lung conditions can also cause it.

Blood from the lungs is often bright red and may be streaked through mucus. Blood that has come from the stomach or mouth needs a different assessment, so describe exactly what happened if you can.

Any coughing up of blood should be assessed promptly. Keep calm, sit upright, and note the colour, amount, whether it was mixed with mucus, and any fever, weight change, chest pain, or breathlessness. Do not take extra doses of blood-thinning medicine to compensate for a missed dose; contact the prescribing team for advice.

A clinician may examine you and arrange imaging, blood tests, or a look at the airways depending on the situation. These tests help identify the source of bleeding.

Seek emergency help now if there is more than a small streak of blood, bleeding continues, breathing becomes difficult, you have chest pain, faintness, confusion, or blue lips. Get urgent assessment even for a small amount if it is new, keeps returning, or occurs with unexplained weight loss or a persistent cough.

Ask what the likely source of the blood is, which tests are needed, whether current medicines affect bleeding, and what symptoms should prompt emergency care.