There are two types of blood in the stool, fresh blood or black blood. The causes of fresh blood in the stool are: hemorrhoids, anal fissure, anal canal cancer, rectal polyps, rectal cancer and other lower gastrointestinal bleeding, and black blood in the stool is caused by upper gastrointestinal bleeding. If there is no pain in the stool, only bleeding, it may be due to hemorrhoids, internal hemorrhoids will be like this. If there is pain during the stool and periodic pain after the stool, then it may be an anal fissure. If the bleeding is caused by rectal polyps, bright red blood but not much, it is common in children. If it is rectal cancer, the frequency of stool will increase, and the early stage of blood in stool will be bright red or dark red, accompanied by a feeling of urgency, thin stool, and weight loss, which should be paid great attention to. You should pay attention to the regularity of life. If it is an anal fissure or hemorrhoid, the pain and blood in the stool will be reduced as long as the stool is clear. If the diagnosis is unknown, you need to go to the hospital for a colonoscopy as soon as possible.