What should you know about coughing up red flem?

Red phlegm often reflects fresh blood mixed through sputum. Repeated coughing can irritate small airway vessels, while pneumonia may inflame the lung and produce blood-streaked mucus. Bronchiectasis may cause bleeding during a flare. A pulmonary embolism, tuberculosis or lung cancer are other possibilities that a clinician may need to consider; the symptom does not identify any one condition.

Check whether the colour is bright red or rust-coloured and whether the mucus is frothy or thick. Keep note of cough duration, fever, chest pain, breathlessness and any recent nose or throat bleeding.

Contact a healthcare professional promptly for advice and explain the colour, amount and frequency. Rest upright, avoid smoking and avoid strenuous exertion while waiting. Do not use someone else’s antibiotics or assume red phlegm is simply a chest infection. A clinician can decide whether examination, imaging or other tests are needed.

Call emergency services if you are short of breath, have sudden chest pain, become faint or confused, or the bleeding is heavy, repeated or difficult to control. Seek same-day care if red phlegm continues, you have a high fever, or you have known lung disease. Take a list of medicines with you, especially medicines that affect clotting.

Ask whether the blood appears to come from the lungs, which warning signs matter most in your situation, whether a medication could contribute, and how to monitor the symptom safely.