What causes coughing up blood?

Blood may appear as streaks mixed with mucus after forceful coughing, but it can also come from inflammation or infection deeper in the airways. Pneumonia, bronchiectasis, tuberculosis, and lung cancer are among the conditions that can present with coughing up blood. A pulmonary embolism can cause blood-stained sputum, especially with sudden breathlessness or chest pain. Blood from the nose, gums, or throat can sometimes be mistaken for blood from the lungs.

The amount, colour, recurrence, and accompanying symptoms matter. A small streak still needs medical advice because the cause cannot be confirmed from appearance alone.

Stop smoking or vaping, avoid strenuous activity until assessed, and note the amount and appearance of the blood. Do not take cough suppressants or blood-thinning medicines for this symptom without medical advice. Arrange prompt clinical assessment, taking a list of medicines and relevant history such as recent infection, travel, surgery, or tuberculosis exposure.

Call emergency services for more than a few streaks, ongoing bleeding, severe breathlessness, chest or upper-back pain, a very fast heartbeat, fainting, confusion, or blue lips. Urgent assessment is also needed if coughing up blood follows an injury or occurs with one-sided leg swelling. Do not drive yourself if you feel faint or struggle to breathe.

Ask whether the blood is likely from the airways or another source, which examination or imaging is needed, and whether your medicines could contribute. Tell the clinician how often it happened, how much you saw, whether it was mixed with phlegm, and whether fever, weight change, pain, or breathlessness accompanied it.