Blood in phlegm and lung cancer

Blood may appear as streaks or may colour the phlegm. Because the source and amount can be difficult to judge at home, any new episode should be reported promptly to a healthcare professional, especially when it recurs or accompanies other breathing symptoms.

Coughing up blood is called haemoptysis. In lung cancer, a tumour may irritate or damage blood vessels in an airway, leading to bleeding. Lung cancer may also present with a persistent or changing cough, breathlessness, chest discomfort, repeated chest infections, or a hoarse voice.

Other explanations include bronchitis, pneumonia, airway widening, a blood clot in the lung, and irritation after forceful coughing. Blood from the nose, mouth, or stomach can sometimes be mistaken for blood coughed up from the lungs, so clinicians first clarify where it came from.

Contact a healthcare professional promptly, even if you see only streaks and otherwise feel well. Note when the bleeding began, whether it has happened again, the approximate amount, the colour, and any fever, chest pain, breathlessness, weight change, or altered cough.

Tell the clinician about smoking or vaping, recent infections or travel, previous lung problems, cancer history, and medicines that affect clotting. Assessment may include an examination, blood tests, chest imaging, or a camera examination of the airways; the choice depends on your symptoms and medical history.

Call emergency services if you cough up more than a few streaks of blood, bleeding continues, or you develop severe breathlessness, chest pain, a very fast heartbeat, dizziness, confusion, or fainting. Sit upright if possible and do not drive yourself.

If you already have lung cancer, report any new blood in phlegm to your cancer team the same day. Treatment, infection, a clot, or the tumour itself may need assessment, and the team can advise whether you should attend an emergency department.

What is the likely source of the blood? Which tests will help identify the cause? Should I change any medicine while bleeding is assessed? Which changes mean I should call emergency services, and whom should I contact if it happens again?