Doing colonoscopy is fine but there is blood in the stool, which may be caused by life factors, drug factors and disease factors. 1. Life factors: if you often have the habit of smoking and drinking, it may lead to upper gastrointestinal bleeding, which may cause dry stools and poor defecation, at this time, the patient will find that he/she has bleeding in stools, but no abnormality will be detected through the examination. At present, no special treatment is needed, and some improvements should be made in daily life. 2. Drug factors: If you have previously taken aspirin, clopidogrel and other drugs, may lead to blood in the stool, these drugs will affect the coagulation function, but through the colonoscopy generally will not find abnormal. No special treatment is needed, and the symptoms will be relieved after stopping the medication. 3. Disease factors: for example, hemorrhoids, small intestine diverticulum, pancreatic diseases, etc., these diseases can lead to a lot of blood, but through the colonoscopy generally can not be detected, should be done as soon as possible to analyze the stool routine examination. If the colonoscopy is fine, the stool has been bleeding, but also to be highly vigilant is due to other diseases, so in addition to colonoscopy, but also to do other tests to analyze.