Hepatitis B generally refers to the hepatitis B virus, and testing for the hepatitis B virus must be performed prior to colonoscopy. Colonoscopy is mainly a clinical method used to observe whether there are lesions in the colon and large intestine area, and it is applicable to unexplained lower gastrointestinal bleeding, chronic diarrhea, and abdominal masses. Usually, patients need to be tested for hepatitis B virus before the examination to avoid cross-infection. Some of the examinees also need to cooperate with the doctor for blood tests, electrocardiogram, etc. They should also cooperate with the doctor for bowel preparation. The 3 days before the colonoscopy are mainly low-fat, fine, fluid soft food with little residue, and 1 day before the examination, eat low-fat, fine, fluid soft food without residue. On the day of the examination, you can follow the doctor’s instructions to use laxatives or enemas to clean the intestines, so as to facilitate smooth colonoscopy and ensure the accuracy of the examination results. Patients with severe heart disease, respiratory failure, peritonitis, etc. are not allowed to undergo colonoscopy. It is recommended to consult a regular hospital for colonoscopy, avoid excessive tension during the examination and actively cooperate with the medical staff.