Fasting in the clinic, generally require at least in the case of no food or drink to maintain more than 8 hours, such as the need to check blood biochemistry, gastrointestinal endoscopy, or the next day there is a surgical case, the patient is required in the previous night after 12:00 pm can not eat, nor can drink water, until 8:00 am the next morning. So when doctors say fasting in the clinic, they mean to keep about 8 hours of total fasting without eating or drinking, so that various checkups can be kept in a more accurate state the next morning. Doing the surgery in a state of fasting can avoid choking caused by reflex vomiting due to the surgical procedure.