Coughing up blood: understanding the differential diagnosis

Coughing up blood needs medical assessment because causes range from irritated airways to serious lung conditions. Blood streaks mixed with mucus can follow forceful coughing, infection or airway inflammation, but the appearance alone cannot identify the cause.

A clinician will check whether the blood was coughed up from the chest or came from the nose, mouth or throat. They may ask about the amount, colour, timing, smoking history, medicines and other symptoms. Chest infection, pneumonia and bronchiectasis can irritate or damage airway tissue. Pulmonary embolism can cause blood with sudden breathlessness or chest pain. Tuberculosis and lung cancer are less common possibilities that require appropriate testing; having blood in sputum does not by itself identify any one condition.

Arrange prompt medical advice, especially if the bleeding returns or you have a long-standing cough. Note when it happened, whether it was mixed with mucus, and any breathlessness, fever, chest pain or weight change. Do not smoke, and do not start or stop a blood-thinning medicine without medical guidance. A clinician may examine your chest and decide whether imaging, blood tests or a sputum sample is needed.

Seek emergency help if bleeding is heavy or persistent, breathing is difficult, you have severe chest pain, feel faint, become confused, or your lips look blue or grey. Urgent assessment is also needed after a recent operation, prolonged immobility or if you take anticoagulants. These warning signs can indicate a problem affecting breathing or circulation.

Ask what source of bleeding seems most likely, which tests are appropriate, and whether any medicines could be contributing. You can also ask what changes should prompt emergency care and when to arrange follow-up.