The 30-second summary
- The advice changed in October 2024, and most people are still hearing the old version. Five societies now say most patients should continue their GLP-1 before elective surgery, rather than stopping it.
- The concern is the stomach, not the drug. GLP-1s slow gastric emptying, and an anaesthetised person with food still in the stomach risks aspiration. Everything in the guidance is aimed at that one problem.
- Higher risk gets a liquid diet, not a cancelled dose. For people most likely to have a full stomach, the guidance suggests clear liquids for 24 hours beforehand.
- Your job is to tell them early. Not on the morning of the operation. When you book it.
What changed, and why you may have been told otherwise
In June 2023 the American Society of Anesthesiologists issued its first consensus advice on this question, and it was cautious: hold the medicine for one dosing interval, a week for a weekly injection and a day for a daily one, then follow the usual fasting rules.
That advice spread quickly, and it is still what many people are told. It was also based on very little, because almost no data existed at the time.
In October 2024 a broader group revisited it. The American Society of Anesthesiologists, the American Gastroenterological Association, the American Society for Metabolic and Bariatric Surgery, the International Society of Perioperative Care of Patients with Obesity and the Society of American Gastrointestinal and Endoscopic Surgeons published joint guidance, and the headline reversed: most patients should continue taking their GLP-1 receptor agonist before elective surgery.
The reasoning is straightforward. Stopping has costs of its own. Blood sugar control slips in people taking these medicines for diabetes. Appetite returns and weight goes back on. And after a gap, restarting at the old dose is poorly tolerated, which is a real harm set against a risk that, for most people, is small.
What the actual risk is
Anaesthesia removes the reflexes that keep stomach contents out of your airway. That is why you are asked not to eat beforehand. If the stomach is still full when you go under, the contents can travel the wrong way and reach the lungs, which is called pulmonary aspiration, and it is serious.
GLP-1s slow the stomach. That is not a side effect, it is the mechanism: food sits longer, you feel full sooner, you eat less. The same property means a standard overnight fast may not empty the stomach as reliably as it would in someone not taking one.
So the guidance is not really about the medicine. It is about making sure your stomach is empty by the time you are asleep, and there is more than one way to achieve that.
Who is higher risk
The guidance names four things that raise the chance of a stomach that has not emptied:
| Higher risk if | Why |
|---|---|
| You are in the escalation phase | Typically the first four to eight weeks, when the dose is climbing and the gut has not adapted |
| You have gastrointestinal symptoms | Nausea, vomiting, abdominal pain, bloating, shortness of breath or constipation |
| You are on a higher dose | The effect on stomach emptying is dose-related |
| You have another cause of slow emptying | For example Parkinson's disease |
If none of those apply, you are in the group the guidance expects to carry on as normal.
What higher risk means in practice
Not a cancelled dose. A clear liquid diet for 24 hours before the procedure, or other measures depending on the circumstances.
This is the sensible part of the guidance and the part most worth understanding. Liquids leave the stomach in a fraction of the time solids take. Twenty-four hours of clear liquids empties the stomach far more reliably than an overnight fast does, and it does it without interrupting treatment at all.
The guidance also asks the anaesthetic team to adapt: adjusting the plan to minimise aspiration risk, and using point-of-care ultrasound immediately before the procedure to look at the stomach contents in the highest-risk patients. An ultrasound takes a minute, and it turns a guess into a measurement.
What to do before your operation
Tell them when you book, not on the day. The single most useful thing you can do is make sure the surgical and anaesthetic teams know which medicine you take, what dose, when your last dose was and whether the dose has changed recently. A decision made a fortnight ahead is a plan. The same decision made at 7am in a gown is a cancellation.
Say whether you have gut symptoms now. Not whether you had them in month one. The guidance keys on current symptoms, and "I have been feeling full and a bit sick this week" changes which group you are in.
Ask three questions. Should I continue my GLP-1? Do you want me on clear liquids for 24 hours? When should my last dose be? Write the answers down; the people you speak to on the day may not be the people who decided.
Ask about restarting. If the operation means missing doses, find out now whether you go back to your usual dose or step back down. Tolerance fades during a break, and returning straight to a maintenance dose after weeks away is one of the more reliable ways to have a genuinely bad fortnight.
Eating around it
On a normal week the job is protein at every meal. In the days before an operation the job changes: follow the fasting or liquid instructions you are given exactly, because those exist for a reason that has nothing to do with nutrition.
Afterwards, appetite is usually poor for a while, from the surgery as much as the medicine. Protein still matters, and healing raises the requirement rather than lowering it. Soft, cold, high-protein things are the ones that go down when nothing else will: Greek yoghurt, skyr, cottage cheese, milk, a soup with lentils or beans blended through it. Small and often beats three meals you cannot face.
What to do with this
If you have an operation or an endoscopy coming up, the practical thing is to know your medicine, your dose and how long you have been on it, and to have those to hand for the pre-assessment call.
Sources
- Kindel TL, et al. Multisociety clinical practice guidance for the safe use of glucagon-like peptide-1 receptor agonists in the perioperative period. Surg Obes Relat Dis 2024. PubMed
- American Society of Anesthesiologists. Most Patients Can Continue Diabetes, Weight Loss GLP-1 Drugs Before Surgery, Those at Highest Risk for GI Problems Should Follow Liquid Diet Before Procedure, 29 October 2024. ASA
- American Society of Anesthesiologists. Consensus-Based Guidance on Preoperative Management of Patients on Glucagon-Like Peptide-1 Receptor Agonists, June 2023. ASA
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