Blood in sputum when coughing needs to consider ear, nose and throat diseases, respiratory diseases, autoimmune diseases, hematologic diseases, etc. Blood sputum should be found with relevant imaging and laboratory tests, and anti-inflammatory, hormonal, targeted therapy, surgery and other treatments should be given according to the different conditions to avoid delayed condition. 1. Ear, nose and throat (ENT) diseases: such as rhinitis/sinusitis, nasopharyngeal carcinoma, oral mucous membrane damage, etc. These lesions located in the upper airway lead to hemorrhage, which flows along the nasopharyngeal structure to the pharyngeal cavity, resulting in blood in sputum. At this time, we should go to the ENT department to clarify the cause of the lesion, and then give anti-inflammatory and surgical treatments for different diseases. 2. Respiratory diseases: acute upper respiratory tract infection, lobar pneumonia, tuberculosis, bronchial dilatation, pulmonary embolism, pulmonary hypertension, lung tumors, etc., can cause blood in sputum, and should be referred to respiratory medicine for diagnosis and treatment. 3. Autoimmune diseases: vasculitis can lead to pulmonary hemorrhage, type I acute nephritis (good-pasture syndrome) can cause blood in sputum; go to the Department of Rheumatology/Nephrology in time for treatment with hormones and cytotoxic drugs. 4. Hematologic diseases: Leukemia, thrombocytopenia, etc. can also cause blood in sputum, which requires targeted therapy, chemotherapy, stem cell transplantation, etc. To sum up, there are many kinds of diseases that lead to blood in sputum, it is difficult to generalize, once found, you should go to the regular hospital for diagnosis and treatment immediately, so as not to delay the condition.