There is blood in the toilet when going to the bowels, divided into upper and lower gastrointestinal bleeding, common causes are hemorrhoids, ulcerative colitis, anal fissure, rectal lesions, peptic ulcers, gastric mucosal injury and malignant tumors. 1. Hemorrhoids: dry and hard feces damage to the surface mucosa of the hemorrhoidal nucleus, there will be the phenomenon of bright red blood dripping out of the stool, and in severe cases, there will be a jet of bleeding performance. 2. ulcerative colitis: ulcerative colitis patients, under the stimulation of inflammation, easily lead to colorectal mucosa erosive bleeding phenomenon. 3. Anal fissure: when the patient is straining to defecate, the wound of the anal fissure is stimulated, and bleeding symptoms will occur, accompanied by severe pain. 4. Rectal polyp when fecal friction stimulation and other reasons lead to polyp mucosa erosion, ulceration, bleeding phenomenon will occur. 5. Upper peptic ulcer: patients with gastric or duodenal ulcers are prone to bleeding symptoms when their condition is serious. 6. Gastrointestinal mucosal injury: in a large number of alcohol abuse, or often take aspirin and other drugs, easy to damage the gastrointestinal mucosa, causing upper gastrointestinal bleeding. 7. Malignant tumors: gastrointestinal bleeding can occur when the surface mucosa of various tumors in gastrointestinal tract undergoes rupture. 8. Other lesions: intestinal parasitic diseases, esophagogastric fundus varices or bleeding, hemophilia, various thrombocytopenic purpura and other diseases, may cause bleeding in the stool. Therefore, if you find bleeding in the stool, it is recommended that you seek medical advice in time to avoid delaying your condition.