Pre Operative Fasting Guidelines for Adults

Why fast before anaesthesia?

Pulmonary aspiration (vomiting and breathing the contents into one’s lungs) during anaesthesia is a rare event and usually occurs in the context of emergency surgery. It is, however, a significant event and sometimes results in death. Fasting guidelines before surgery, are designed to reduce this occurrence. Guidelines apply to patients having elective surgery and are intended for procedures performed under general (sleeping) anaesthesia local anaesthesia or sedation. Aspiration may occur during any kind of anaesthetic or sedation if the stomach is not empty because anaesthetic or sedative medications reduce our ability to cough, and also increase the likelihood of being sick when lying down.

Emergency surgery

Circumstances will vary from person to person. In general if you have an acute medical problem and you are going to go to accident and emergency or think that you might have a chance of an emergency procedure, then you should stop eating completely. Your doctor may allow you to have sips of water up to four hours before the possible anaesthetic.

Elective surgery

Do not eat in the six hours before anaesthesia and prior to that the last meal should be light. Do not consume milky drinks food lollies jelly or chewing gum for six hours before anaesthesia. You can consume water in small volumes (up to 200mls or one cup) up to two hours before surgery. Do not drink anything in the two hours prior to anaesthesia except for a sip of water to swallow medications if required.


Please take all of your normal medications unless otherwise instructed by Dr Thomas or the anaesthetist. Specialist circumstances may apply to diabetic tablets. In general the default is to cease any kind of tablet that may “thin the blood” such as aspirin clopidogrel etc. at least one week before surgery. If you are taking anticoagulants such as Xarelto or Warfarin specific instructions will be required from your anaesthetist surgeon in consultation with a haematologist.

Patients with a specific admission time

This will apply to most patients who will be given a fairly clear idea of when the operation is to take place although this always varies due to operational requirements on the day.

Morning operation

Operating lists tend to start at 8am. Do not eat after 2am. Do not consume milk food lollies jelly or chewing gum after 2am. You may drink clear fluids in quantity up to 200mls until 6am. Do not drink anything after 6am except for a sip of fluids to swallow medications.

Afternoon Operation

Lists start at 1.30pm. Do not eat after 7am including mild drinks food lollies jelly or chewing gum. You may drink clear fluids in quantities up to 200mls until 11am. Do not drink anything after 11.30am except for a sip of fluid to swallow medications if required.


Clear fluids are fluids which are transparent and they include glucose based drinks, cordials and clear juices. They do not include milk based or particulate products such as orange juice, Up and Go or Sustagen. Chewing gum stimulates saliva secretion and gastric secretions. If it is not swallowed, it could be considered a clear fluid however occasionally chewing gum is swallowed, and if this is the case it must be regarded as solid food and so the six hour rule applies.

Special situations 

  1. Obesity or prior gastric reduction/lap banding etc. Standard fasting guidelines apply for preoperative patients with raised body mass index. In most studies gastric emptying of both liquids and solids is not delayed in these patients. Fasting guidelines should be followed to the letter in patients with previous lap banding etc., the last meal prior to anaesthesia should be light.
  2. Pregnancy. Standard fasting guidelines apply for the preoperative patient who is not in labour. Gastric emptying is normal.
  3. Diabetes. Patients with diabetes have an increased chance of delayed gastric emptying. Your preoperative oral hypoglycaemic and insulin requirements will need to be discussed with the anaesthetist and you will also be advised if different fasting guidelines apply.