Blood in the stool may be cancer, but not necessarily cancer. Blood in the stool can be caused by many diseases, such as peptic ulcers, including gastric ulcers and duodenal ulcers, colon lesions including gastrointestinal tumors, ulcerative colitis, Crohn’s disease, hemorrhoids, etc. Usually most of the blood in the stool comes from the lower gastrointestinal tract, that is, colon, anus, and rectal lesions. However, upper gastrointestinal bleeding can also cause blood in the stool if the bleeding volume is relatively large. In order to clarify the cause, a gastroscopy should be completed to finally confirm what disease is causing it. If blood in the stool is accompanied by symptoms such as lethargy, poor nutrition, weakness, decreased physical strength, anemia, etc., one must be highly alert to the possibility of cancer, which may come from the upper gastrointestinal tract such as the stomach, or from the colon, etc.