Fasting for your operation – Why?

Most of us enjoy our food and coffees ( your anaesthetists included), so fasting is never much fun. However there are good reasons as to why we ask you or your child to fast before your operation.

As you “go off to sleep”, the initial part of your anaesthetic we call “induction”, there is a small chance that you could either vomit or regurgitate some of the fluid in your stomach into your throat. Even more rarely some of this fluid can go down into your lungs, something we call “aspiration”. This can cause a variety of lung complications ranging from a bit of a cough and fever all the way through to a severe lung infection.

If you happen to have a full stomach; you are both more likely to vomit or regurgitate during induction and if any of the vomit was to go into the lungs it would be more likely to cause complications. This is why we ask you to fast before your surgery

You are probably thinking “ what happens when someone has just eaten and is then involved in some sort of accident that requires surgery ?” This is not an uncommon occurrence at all and in these cases we weigh up the risks of doing the emergency surgery with a full stomach, and the risk of waiting till the patient is fasted. These decisions are individualised for every case we do and in many cases we operate on a patient with a full stomach as this is in the patient’s best interest. Even in these cases it is very rare for there to be any complications from a full stomach.

In elective surgery ( the most common form ) we always try and stack the odds to minimise any risks of complications occurring so this is why we ask you to fast for your surgery.


  1. Solid food and baby formulae six hours fasting.
  2. Clear fluids ( eg apple juice, black coffe or tea ie no milk ) and breast milk four hours fasting.
  3. Water only two hours fasting.

In terms of what to eat, if you have been told to fast from midnight the night before your morning surgery then you may have a normal meal the night before. I would not advise going out to Pizza hut and eating five pizzas ! but a normal healthy meal is fine. For breakfast it is fine to have cereal, fruit and toast. Poached or boiled eggs are also a good idea, again however McDonalds or Bacon and eggs should sensibly be avoided.

We would encourange you to continue drinking water up until the time you have been given as this will lessen the chances of you feeling dehydrated or nauseous.