Coughing up dark red blood: what to know

Blood can look dark after it has mixed with mucus or remained in the airways for a while. The source may be irritation from forceful coughing, an infection such as Pneumonia, or a longer-term airway problem such as Bronchiectasis. Less common but serious causes include Pulmonary Embolism, Tuberculosis, or Lung Cancer. The colour alone cannot identify the cause, and swallowed blood from the nose or mouth can sometimes be mistaken for blood from the lungs.

Arrange prompt medical advice, even if the amount seems small. Note when it started, whether the blood was mixed through mucus or appeared separately, and whether it has happened before. If possible, keep a clear description or photograph for the clinician. Do not smoke, exercise heavily, or take a medicine that affects clotting unless the prescriber has told you to continue it; seek advice before changing prescribed treatment. A clinician may listen to your chest and decide whether tests are needed.

Seek emergency help if bleeding is heavy or ongoing, breathing becomes difficult, you have chest pain, faintness, confusion, a fast heartbeat, or blue-grey lips. Urgent assessment is also needed after a recent operation, prolonged immobility, or a known clotting problem. Do not drive yourself if you feel faint or short of breath; keep upright and take any medication list with you.

Ask what part of the respiratory tract may be bleeding, whether an infection or airway condition fits your other symptoms, and which warning signs should bring you back urgently. Ask whether any inhalers, blood-thinning medicines, or recent travel change the assessment.