When should you see a doctor about coughing up blood?

Blood may come from irritated airways after forceful coughing, an infection such as pneumonia, or a condition affecting the bronchial tubes such as bronchiectasis. Less common but serious causes include pulmonary embolism, tuberculosis, or lung cancer. Blood from the nose, mouth, or stomach can sometimes be mistaken for blood from the lungs, so describe exactly what happened.

Stop exertion, sit upright, and note the colour, amount, timing, and whether it was mixed with mucus. Do not drive yourself if you are breathless, faint, or deteriorating. Take a list of medicines, especially blood thinners, and tell the clinician about fever, leg swelling, recent travel, smoking, infection exposure, or previous lung disease.

Call emergency services for heavy or repeated bleeding, severe breathlessness, chest or upper-back pain, a fast heartbeat with weakness, fainting, confusion, or blue lips. Even a small streak should be assessed promptly if it recurs or comes with fever, night sweats, unexplained weight loss, or a new persistent cough.

Ask where the blood may be coming from, whether you need chest imaging or other tests, and which medicines to continue. If a serious cause is found, ask how treatment controls the bleeding and what follow-up symptoms require immediate help.