Patients with gastrointestinal bleeding can be clearly diagnosed as having gastrointestinal bleeding if there is vomiting of blood and black stool, along with routine blood tests that suggest a decrease in hemoglobin or positive stool occult blood or the presence of red blood cells. Patients with gastrointestinal bleeding need to be differentiated as follows: 1. Pay attention to the differentiation between vomiting and hemoptysis. If a patient presents with vomiting blood accompanied by coughing and coughing sputum, attention should be paid to identifying whether it is vomiting blood or hemoptysis, and whether the bleeding is caused by pulmonary disease or gastrointestinal digestive tract disease. Such patients need detailed medical history and chest imaging; 2. Pay attention to identify whether the bleeding is caused by the mouth, nose, throat and other parts of the body, and need to conduct detailed physical examination and careful medical history; 3. Pay attention to identify whether it is a pseudo-black stool caused by food or drugs, etc. Patients who take iron or pig liver, pig blood, bismuth and other food conditions may also have black stool.