Coughing up bright red blood, also known as hemoptysis, may be caused by a variety of reasons, such as respiratory diseases, circulatory diseases, hematologic diseases, infectious diseases, trauma, etc., and the specific cause of the disease should be clarified after timely consultation. 1. Respiratory system diseases. Including bronchial diseases, such as bronchodilatation, bronchopulmonary cancer, endobronchial tuberculosis, etc., leading to rupture of blood vessels under the bronchial mucosa and bleeding; lung diseases, such as tuberculosis, lung cancer, pulmonary embolism, etc., which may lead to hemoptysis if the lesions invade the pulmonary artery and other blood vessels. 2. Circulatory system diseases. Such as congestive heart failure, mitral stenosis, pulmonary hypertension, etc., because these diseases can lead to pulmonary stasis, which can cause endobronchial capillary rupture and hemoptysis. 3. Blood system diseases. Such as hemophilia, thrombocytopenic purpura, aplastic anemia, leukemia, etc., may also lead to hemoptysis. 4. Infectious diseases. Such as epidemic hemorrhagic fever, leptospirosis, etc., may also appear hemoptysis. 5. Trauma. Such as chest contusion, rib fracture, etc., or other parts of the injury has been thoracentesis, lung puncture and other operations. In serious cases, it is recommended to actively seek medical treatment and follow the doctor’s instructions.