The first thing to note is to rule out the presence of food and drug factors, such as eating red food, dragon fruit, animal offal, drug factors including bismuth pectin, may appear dark red stool. In addition, whether there is a combination of gastrointestinal bleeding, then you can do a routine stool examination to understand whether the occult blood is positive, and check the blood routine to observe whether the hemoglobin drops. If the presence of gastrointestinal bleeding is clear, gastroscopy, colonoscopy and capsule endoscopy can be done to clarify the cause of bleeding, whether it is caused by peptic ulcer, gastric cancer, gastrointestinal tumor, small intestine lymphoma, colon cancer and other factors that cause dark red stool, and to use the right medicine for the cause.