Fasting Guidelines

General Fasting Guidelines

Before surgery, you should stop eating and drinking so your stomach is empty. This helps keep you safe while you’re asleep.

Here’s what to remember

  • Clear drinks (water, clear juice, tea/coffee without milk)

  • You can drink up to 2 hours before your anesthesia.

  • Stop solid food 6 hours before anesthesia.

Why this matters

Your stomach needs to be fairly empty so you don’t accidentally inhale food or drink into your lungs while asleep — that could be dangerous.

Patients on GLP-1 agonists

GLP-1 agonists are medicines that slow down how quickly your stomach empties, which means food or liquid might stay in your stomach longer than usual. That can make it more likely that stomach contents could travel back up into the windpipe during anaesthesia — which is why extra care is needed with fasting.

The key recommendations from ANZCA 2025 guidelines

  1. You should not stop taking your GLP-1 medicine unless your doctor tells you to.Stopping them abruptly can make blood sugar or weight management worse.

  2. A 24-hour period before surgery where you only have clear fluids (e.g., water, pulp-free juice, clear tea/coffee without milk).

  3. Then follow the standard fasting rules — no solids for at least 6 hours and limited clear fluids until about 2 hours before anaesthesia.

This extra period of only clear fluids is intended to help reduce stomach contents because the drug slows digestion.

If you cannot manage the 24-hour clear fluid diet, or if doctors are still worried your stomach isn’t empty, they may use other techniques — like a quick ultrasound to check your stomach contents or give medicines that help speed up stomach emptying.

Why this matters

If the stomach isn’t empty when anaesthesia starts, there’s a higher risk of stomach contents going into the lungs, which can cause serious problems. The longer clear-fluid only period aims to reduce that risk.