Patients with blood in stool need to do the following tests: 1) routine stool with occult blood test to clarify whether the stool is blood; 2) e-colonoscopy or e-gastroscopy to clarify the cause and site of bleeding. If the stool is fresh blood, it is most likely that there is bleeding in the area below the colon, and an e-colonoscopy is needed to clarify. If the blood in the stool is dark red, it is likely to be bleeding from the area above the colon, such as the small intestine, duodenum, or stomach, and an electron gastroscopy or small intestine microscopy is needed to clarify. In addition, to determine the amount of bleeding, blood tests and reticulocyte ratios are needed to clarify. If the bleeding exceeds 1000ml, the patient’s blood pressure drops, heart rate increases and other shock-like symptoms, the patient’s blood type needs to be clarified and transfused as soon as possible to maintain the patient’s blood volume.