Diseases that cause coughing up blood are not limited to respiratory diseases, although a major coughing up blood is a common disease in the respiratory system. There are many diseases that cause coughing up blood, and the common diseases are as follows: First, the most common are respiratory diseases, such as tuberculosis, bronchial dilatation, lung cancer, and various infections of the lungs, which are more common causes of coughing up blood, and the first thing to consider is the lung diseases. Second, not lung diseases, can be seen in other system diseases, the most common such as circulatory system diseases, that is, the cardiovascular system, such as wind heart disease mitral stenosis, hypertension, heart disease, pulmonary hypertension. Third, trauma, coughing up blood after an injury to the chest. Fourthly, systemic diseases with bleeding tendency, such as hematological diseases, leukemia, hemophilia will appear this kind of bleeding, bleeding of various systems. The fifth is some other rare diseases, such as pulmonary hemorrhage, nephritis syndrome, which is a small vasculitis, which leads to bleeding of small blood vessels throughout the body, not only in the lungs, but also in the kidneys. So for coughing up blood, in addition to knowing that lung diseases are the most common, you should also know that many other systemic diseases can lead to coughing up blood, and you should go to the hospital in a timely manner to identify the cause of coughing up blood through the appropriate tests and treat it accordingly.