The answer is yes, not only do you need to fast, but you also need to do a bowel prep. Think about the pipeline is of course in the absence of any impurities when easy to observe, then the intestinal tract is also needed to clean up after in order to see more clearly. Here we talk about the clinical as intestinal preparation of drugs and the use of methods: 1, compound polyethylene glycol electrolyte bulk for clinical use, the best safety. Open a box with A dose and B dose, generally A dose B dose are open to a cup with 1000ml cool warm water (hot water may lead to more foam in the intestinal lumen), generally within 1 hour in 3-4 times to drink, you can first fast and then slow, the first half hour of 800ml or so, followed by every 15 minutes to drink on the 300 ml. Drinking more walking, generally should be running to the toilet. There is also said to drink a box the night before, and then drink a box the next morning for better results. 2, mannitol injection 20% 250ml mannitol 2 bags plus 500ml sugar saline 1 bag, first drink mannitol and then drink sugar saline, drink within 1 hour. If there is nausea and vomiting in the process of drinking, you can slow down the speed of taking. The disadvantage is that in the process of doing colonoscopy if found polyps, bleeding can not use electrocoagulation or electrocision, because there may be a risk of gas explosion. 3, magnesium sulfate Because I have not applied magnesium sulfate in the clinic, I just heard the teacher say that magnesium sulfate is also used in the preoperative preparation of colonoscopy. General colonoscopy are in the afternoon, there is information about colonoscopy 4-6 hours before the examination (usually around 8 am that day) to start taking the drug, 50g of drugs plus 100ml of warm boiled water, followed by oral intake of warm boiled water 2000-2500ml. 4, sodium phosphate This drug is often used in my clinic, the use of: 8:00 p.m. the day before the examination to drink a (45ml) plus 800ml of warm and cooled boiled water, and then drink a (45ml) plus 800ml warm boiled water. At 8:00 a.m. on the same day, drink another plus 800ml of warm, cool water. On the day of the examination, fasting is prohibited after 12 o’clock, and water is prohibited. Colonoscopy generally need to make an appointment, and with the improvement of modern medical service level, hospitals will improve the precautions before doing colonoscopy such as: in the diet, in the first three days before the examination, it is best to eat liquid food, it is best not to eat high-fiber food (because these foods are difficult to digest); in the medication, patients with high blood pressure can take blood pressure-lowering drugs. The hospital will also provide a list of ways to take medication.