Coughing up blood is generally called hemoptysis in medicine, which is a more urgent and serious symptom of the respiratory system, specifically referring to bleeding from parts below the larynx, such as the trachea and bronchi, and then expelled from the body through the action of coughing. Coughing up blood can be seen in many common diseases, including the following: 1. bronchiectasis: bronchiectasis causing hemoptysis is one of the most common clinical causes, mostly in young adults, but also in the elderly, often accompanied by coughing up pus sputum, the amount of hemoptysis can be more or less. 2. tuberculosis: tuberculosis can cause hemoptysis, especially cavitary tuberculosis, in addition to coughing up blood, can also cause night sweats, low fever, wasting and other symptoms. 3: Lung cancer, mostly seen in the elderly who have been smoking for a long time, coughing up blood is generally less, blood in sputum is more common, and can be accompanied by weight loss, enlarged peripheral lymph nodes and chest pain. 4: Pharyngitis: coughing up blood caused by pharyngitis is mostly blood in sputum, caused by the rupture of capillaries in the throat, most of which can stop on their own. 5: Pneumonia and bronchitis can also cause coughing up blood, but the amount of coughing up blood is generally very small. Therefore, it is necessary to improve the CT examination of the lungs to identify the cause of coughing up blood.