Flu and coughing up blood: what to know

Small streaks may come from irritated airways after forceful coughing, but blood can also occur with pneumonia, bronchiectasis, tuberculosis, a blood clot in the lung, or lung cancer. Blood from the nose, gums or throat can be mistaken for blood coughed from the chest. Note whether it is bright red, mixed with mucus, or accompanied by clots, and whether it followed vomiting rather than coughing.

The amount, recurrence and associated symptoms matter more than trying to diagnose the cause at home. Breathlessness, chest pain, a fast heartbeat, faintness or one-sided leg swelling raise concern for an urgent problem.

Stop strenuous activity, sit upright, and arrange medical advice promptly even if the blood is only streaking. Do not suppress the cough with leftover prescription medicine. Keep a note or photograph of the sputum if safe, and bring a list of medicines, including blood thinners. Avoid smoking and do not drive yourself if dizzy, breathless or faint.

Call emergency services immediately for more than a few streaks, repeated bleeding, clots, severe breathlessness, chest or upper-back pain, fainting, confusion, or blue lips. Urgent assessment is also needed when coughing blood follows prolonged immobility, recent surgery, or a painful swollen leg. Do not wait for a routine appointment when these signs are present.

Ask where the blood may be coming from, whether you need chest imaging or other tests, whether any medicine increases bleeding, and which symptoms mean you should return straight away.