Blood in sputum without coughing may be caused by bleeding gums, nasal bleeding, lung tumors, tuberculosis, bronchodilatation combined with infection, chronic lung abscess, mitral stenosis and other reasons. 1. Gum bleed: when there is blood in the sputum without coughing, it is very likely to be caused by gum bleed. 2. Nasal bleeding: Since the nasal cavity and the oral cavity are connected with each other, blood in the sputum may be caused by nasal bleeding, and the patient usually will not have coughing symptoms in this case. 3. Lung tumor: In lung cancer patients, if the tumor invades local blood vessels, it may cause hemoptysis, resulting in blood in sputum. 4. Tuberculosis: besides causing blood in sputum, tuberculosis may also bring about fever, tiredness, night sweating and other symptoms. 5. Bronchial dilatation combined with infection: bronchial dilatation will not only cause recurrent infections, but also bring recurrent hemoptysis symptoms, the formation of blood in the sputum does not exclude the possibility of bronchial dilatation. 6. Chronic lung abscess: hemoptysis is one of the common symptoms for patients with chronic lung abscess, so this disease may also cause blood in sputum. 7. Mitral stenosis: Mitral stenosis is a heart disease that prevents blood from flowing smoothly from the left atrium to the left ventricle, resulting in blood in the sputum, which may cause hemoptysis in severe cases. If you have blood in sputum only occasionally and have no other discomfort, you generally do not need to worry too much, but if you have blood in sputum for a long period of time, it is recommended that you consult a doctor as soon as possible for diagnosis.