Surgery, endoscopy and anaesthesia

Almost every warning about GLP-1 medicines concerns how you feel. This one concerns something you would never notice, in a situation where you are unconscious, and it is the reason anaesthetic societies issued specific guidance about this class.

It is also the single most commonly forgotten disclosure. People remember to mention a GLP-1 to their prescriber and forget to mention it to the dentist arranging sedation, or to a surgical pre-assessment nurse working from a form that does not ask.

The problem

Before anaesthesia or sedation you are asked to fast. The purpose is to ensure the stomach is empty, because under sedation the reflexes that keep stomach contents out of your lungs are suppressed. If contents are regurgitated and enter the airway — aspiration — the consequences range from serious to life-threatening.

Standard fasting periods are built on how quickly a normal stomach empties. GLP-1 medicines slow that process deliberately, and there are documented cases of patients who fasted correctly and were nonetheless found to have substantial retained stomach contents at endoscopy or induction.

The delay is most pronounced during escalation, when levels are still climbing, and after a recent dose. It varies between people in ways that cannot be predicted from the outside.

What usually happens

Guidance from anaesthetic societies has converged on a broadly consistent approach, with the specifics left to the clinical team:

• Holding the medicine before the procedure. For weekly products this typically means skipping a dose; for daily ones, holding on the day. The interval depends on the product's half-life and on the type of procedure.
• A longer or modified fast, sometimes with a clear-liquid diet for a period beforehand.
• Ultrasound assessment of the stomach before induction in some centres, which answers the question directly rather than assuming.
• Modified anaesthetic technique where the risk is judged higher — measures that reduce aspiration risk during induction.
• Postponement, occasionally, for elective procedures where the timing can simply be moved.

Emergency surgery

There is no opportunity to hold a dose in an emergency, which makes the disclosure even more important. If you are ever admitted acutely, make sure the team knows you take a GLP-1 — and if you are not in a position to tell them, a card in your wallet or a medical ID does it for you.

This is a genuinely worthwhile precaution and takes five minutes to arrange. Write the product name, the dose, and the prescriber's contact on a card and keep it with your identification.

Dental procedures

Worth singling out because it is the most frequently missed. Routine dental work under local anaesthetic is not affected. Anything involving sedation is, and dental practices do not always ask about medicines in a way that surfaces this one.

Volunteer it. "I take a weekly GLP-1 injection" is enough to start the right conversation.

Endoscopy and colonoscopy

Both are directly relevant. An endoscopy examines a stomach that may not be empty, and food present obscures the view — which can mean the procedure is abandoned and rebooked, wasting a preparation nobody enjoys. Colonoscopy preparation depends on gut transit, which is also slowed.

Tell the endoscopy unit when you book. They deal with this routinely now and have protocols for it.

Afterwards

Two things are worth anticipating. Restarting the medicine happens on the team's timetable rather than yours, particularly after abdominal surgery. And if you have been unable to eat normally for several days, the interaction between recovery, reduced intake and a medicine that suppresses appetite is worth raising rather than assuming it will sort itself out.

If several doses have been missed by the time you restart, the ladder may need to be rebuilt rather than resumed — tolerance falls faster than it was gained.

The rule, in one line

If someone is going to sedate you, they need to know you take this medicine — and they need to know before the day, not as you are being wheeled in.

A card in your wallet

The scenario this page cannot help with is the one where you are not able to tell anyone. A card carried with your identification solves it in five minutes: the product name, the dose, the day you take it, and your prescriber's contact details.

Emergency teams look for exactly this, and a medical ID on your phone's lock screen serves the same purpose. It costs nothing and it covers the one situation where the disclosure matters most and you cannot make it yourself.

Related

• Who should not take a GLP-1 — The absolute exclusions, the conditions that require caution, and the medicines that need rethinking before you start.
• Pancreatitis: what to watch for — Rare, serious, and easy to dismiss when nausea and abdominal discomfort have become normal. How to tell the difference.
• Drug interactions on a GLP-1 — A slower stomach changes how every oral medicine is absorbed. For most that is irrelevant — for a handful it is not, and those are worth knowing by name.
• Pregnancy, contraception and fertility — Weight-management GLP-1s are not for use in pregnancy — and a slower stomach can affect the pill. Two facts that together catch people out.

Which medicine you are on

Everything above applies across the class, because it comes from a shared mechanism. The numbers that differ — dose ladders, missed-dose windows, in-use storage periods, half-lives — differ by product, sometimes substantially. Each medicine has its own reference here:

Ozempic · Wegovy · Mounjaro · Zepbound · Rybelsus · Saxenda · Victoza · Trulicity · all medicines