How many centimeters of colonoscopy into the intestine also depends on personal factors, generally 70 to 90 cm more, sometimes up to 100 cm, and the height of the patient has a certain relationship. Note that you need to fast before the colonoscopy, the examination will be injected with anesthesia, will not feel the pain. The colonoscopy will enter through the anus, then rectum and large intestine, and the doctor can observe the internal conditions of the colon and large intestine, which is usually used to diagnose the internal lesions of the large intestine and colon. Colonoscopy is required when suffering from colon polyps, chronic colitis, colon cancer, inflammatory diseases of the colon, ulcerative colitis and other diseases. Colonoscopy cannot be done when suffering from anal fissures and perianal cysts. You cannot eat fruits and vegetables three days before colonoscopy, and you need to take iron supplements. If there are symptoms of blood in the stool and abdominal pain after colonoscopy, you should communicate with the doctor in time to avoid accidents.