Sometimes you should not eat or drink before surgery or other medical interventions. It depends on what kind of surgery you have and what kind of anesthesia you need. Here you can find more information on why cant you eat before surgery . Before an elective surgery or other medical intervention, your doctor or nurse will ask you not to eat or drink anything. If you are going to have a local anesthetic, you probably won't need to fast. Local anesthesia numbs a small area of ​​the body and can be given as an ointment, spray, gel, or injection.