GLP-1s before surgery: the aspiration-risk guidance, explained

Why anaesthetists worry about GLP-1 drugs

Before general anaesthesia or deep sedation, patients fast so that the stomach is empty. Under anaesthesia the reflexes that protect the airway are switched off, and if stomach contents come back up they can be inhaled into the lungs, a complication called pulmonary aspiration that can cause pneumonia or worse.

GLP-1 receptor agonists, including semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound) and liraglutide, slow the emptying of the stomach; that is part of how they reduce appetite and blood sugar spikes. A 2024 review explains that this effect is strongest early in treatment and after dose increases, fades with prolonged use for many people, and matters less in people whose stomachs already empty slowly ¹. As use of these drugs grew, anaesthetists and endoscopists began reporting patients who had fasted correctly yet still had food in their stomachs.

What the labels say

Each of the main US labels now carries a warning headed 'Pulmonary Aspiration During General Anesthesia or Deep Sedation' ^{2 3}. Wegovy's says the drug delays gastric emptying and that there have been rare postmarketing reports of aspiration in patients on GLP-1 drugs having elective procedures, who had food left in the stomach despite reportedly following fasting instructions ². It then says something important: available data are insufficient to inform recommendations to reduce the risk, including whether changing fasting rules or temporarily stopping the drug would reduce retained stomach contents ².

The instruction the labels do give is simple: patients should tell their healthcare providers about any planned surgery or procedure if they are taking the drug ^{2 3}. The labels do not tell patients to stop beforehand. That is consistent with the guidance that followed.

How the advice changed

In June 2023 the American Society of Anesthesiologists issued consensus-based guidance advising that weekly GLP-1 injections be held for a week before elective procedures and daily doses on the day of the procedure ⁴. It was the first widely followed rule, but it rested on little evidence, and stopping these drugs has its own costs: blood sugar can rise in people with diabetes, weight-loss treatment is interrupted, and restarting can bring back nausea.

In October 2024, five societies, the ASA, 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 that most patients should continue their GLP-1 drugs before elective surgery ^{5 6}. Patients at the highest risk of gastrointestinal side effects should follow a liquid diet for 24 hours before the procedure, the team can adjust the anaesthetic plan and use point-of-care ultrasound to check the stomach, and in rare cases a procedure should be delayed ⁵. The ASA's release also said that withholding the drugs only from patients with obesity could amount to bias and should be avoided ⁵.

Other countries reached similar conclusions in 2025. A UK multidisciplinary consensus recommended that patients continue these drugs, with full risk assessment and techniques to reduce aspiration risk, decided jointly with the patient ⁷. Australian and New Zealand societies recommended continuing them and advised a 24-hour clear-fluid diet followed by the standard six-hour fast for everyone taking them ⁸. A further US consensus led by the Society for Perioperative Assessment and Quality Improvement noted how much earlier statements had varied, and set out its own recommendations on medication and fasting times ⁹.

What the evidence actually shows

The research pattern is consistent: more food left in the stomach, but no clear rise in aspiration. A meta-analysis of 23 observational studies, covering 262,018 patients having upper gastrointestinal endoscopy, found residual gastric contents about 4.5 times as common in GLP-1 users, and procedures stopped early about 4.5 times as often, but no significant difference in aspiration pneumonia ¹⁰. A scoping review found that seven of eight studies comparing users and non-users reported significantly more residual contents in users, but that almost every report of aspiration involved other risk factors, such as diabetes, reflux, sleep apnoea or other drugs that slow the stomach ¹¹.

That is why the guidance focuses on identifying the patients at highest risk rather than stopping the drug for everyone. Aspiration is rare, the studies are observational, and residual contents are a warning sign rather than the outcome itself. The labels' statement that data are insufficient to guide prevention is an honest summary ².

Who is at higher risk

The multi-society guidance and its accompanying statements point to the situations in which delayed stomach emptying is most likely: early in treatment and during dose escalation, at higher doses, with weekly rather than daily drugs, and in people who currently have gastrointestinal symptoms such as nausea, vomiting, bloating or constipation ^{5 4}. The 2024 review adds that diabetes itself, independent of the drug, can slow the stomach ¹, and the scoping review lists other contributors, from reflux to medicines such as opioids ¹¹.

Your anaesthesia team will weigh these alongside the procedure itself: a short sedation for a colonoscopy differs from a long general anaesthetic, and an emergency operation differs from a planned one.

Endoscopy and colonoscopy

Much of the evidence comes from endoscopy, where the doctor can see the stomach directly. That is where retained food was first noticed, and where it has the most practical consequence: in the meta-analysis, procedures had to be stopped early about 4.5 times as often in GLP-1 users, because food blocked the view or posed a risk ¹⁰. A stopped procedure means repeating the preparation, the sedation and the appointment.

The multi-society guidance covered endoscopy as well as surgery, and the same principles apply: most patients can continue, and those at higher risk may be asked to follow a liquid diet the day before ^{5 6}. Colonoscopy brings its own preparation, usually a clear-liquid diet and bowel cleansing, which some teams adjust for patients on GLP-1 drugs. Ask your endoscopy unit what it wants you to do.

If you are told to pause: restarting safely

Some teams still ask some patients to hold a dose. If that happens, ask exactly when to take the last dose and when to restart, because the labels have specific rules for missed doses that differ by drug. Wegovy's label says that if two or more consecutive weekly doses are missed, the dose should be re-escalated from a lower level to reduce gastrointestinal side effects ². Zepbound's says a missed dose can be taken within four days; after that it should be skipped and the next dose taken on the usual day ³. A pause that runs to two or more weekly doses therefore may not mean simply picking up where you left off; your prescriber decides how to restart.

Questions to ask before a procedure

The single most useful step is the one the labels name: tell the surgeon, anaesthetist or endoscopist, well in advance, that you take a GLP-1 drug, which one, what dose and when you last increased it ². Then ask:

• Should I keep taking my medicine as usual, and if not, when exactly should I take my last dose and restart?
• Do you want me to follow a liquid or clear-fluid diet the day before, and from what time?
• I have recently started or increased my dose, or I have nausea or bloating: does that change the plan or the date?
• If I have diabetes, what should I do about my other diabetes medicines and blood sugar checks?

Guidance differs between countries and hospitals, and it is the team doing the procedure that decides. Do not stop, skip or change a prescribed drug on your own because of something you read, including here.

A note on research and compounded products

Everything above concerns the approved drugs. People using compounded or research versions of semaglutide, tirzepatide or retatrutide face the same stomach-emptying effect with less certainty about dose, and should tell their team exactly what they take. Our guide to compounded, branded and research tirzepatide explains the differences, and our GLP-1 transition hub covers switching and stopping safely under supervision.

Frequently asked questions

Should I stop Ozempic before surgery?

Not on your own. Since October 2024, US multi-society guidance says most patients can continue GLP-1 drugs before elective surgery, with extra precautions for those at higher risk. Tell your surgical and anaesthesia team you take it and follow their instructions.

Why do GLP-1 drugs matter for anaesthesia?

They slow stomach emptying, so food can remain in the stomach after a normal fast. Under anaesthesia, stomach contents can be inhaled into the lungs, although reported cases are rare.

What does a 24-hour liquid diet mean before surgery?

Some guidance advises patients at higher risk to have only liquids for the day before a procedure, then follow the usual fasting rules. Your team will say whether it applies to you and what liquids are allowed.

Do GLP-1 drugs increase aspiration risk?

Studies show they make leftover stomach contents more common, but a meta-analysis of endoscopy studies found no significant increase in aspiration pneumonia. The labels say data are insufficient to know how best to reduce the risk.

Related on Grey Peptides

• Semaglutide
• Tirzepatide
• GLP-1 transition hub

Sources

1. Jalleh, R. J., et al. (2024). Clinical Consequences of Delayed Gastric Emptying With GLP-1 Receptor Agonists and Tirzepatide. J Clin Endocrinol Metab, 110(1), 1-15. PMID: 39418085
2. Novo Nordisk. Wegovy (semaglutide) US prescribing information, section 5.10 (DailyMed set ee06186f, effective June 18, 2026); read October 3, 2026. Ozempic (effective January 30, 2026) carries the same warning as section 5.9.
3. Eli Lilly. Zepbound (tirzepatide) US prescribing information, section 5.9 (DailyMed set 487cd7e7, effective August 28, 2026); read October 3, 2026. Mounjaro (effective August 27, 2026) carries the same warning as section 5.9.
4. Becker's ASC Review. ASA no longer advises holding GLP-1 patients pre-op: 4 things to know. October 2024 (reporting the 2023 hold advice and the 2024 change). Read October 3, 2026.
5. American Society of Anesthesiologists. New multi-society clinical practice guidance released (GLP-1 receptor agonists before elective surgery). News release, October 2024. Read October 3, 2026. ASA
6. Kindel, T. L., et al. (2025). Multisociety Clinical Practice Guidance for the Safe Use of Glucagon-like Peptide-1 Receptor Agonists in the Perioperative Period. Clin Gastroenterol Hepatol, 23(12), 2083-2085. PMID: 39480373
7. El-Boghdadly, K., et al. (2025). Elective peri-operative management of adults taking glucagon-like peptide-1 receptor agonists, glucose-dependent insulinotropic peptide agonists and sodium-glucose cotransporter-2 inhibitors: a multidisciplinary consensus statement: A consensus statement from the Association of Anaesthetists, Association of British Clinical Diabetologists, British Obesity and Metabolic Surgery Society, Centre for Perioperative Care, Joint British Diabetes Societies for Inpatient Care, Royal College of Anaesthetists, Society for Obesity and Bariatric Anaesthesia and UK Clinical Pharmacy Association. Anaesthesia, 80(4), 412-424. PMID: 39781571
8. Hocking, S. L., et al. (2025). 2025 ADS/ANZCA/GESA/NACOS clinical practice recommendations on the peri-procedural use of GLP-1/GIP receptor agonists. Anaesth Intensive Care, 53(5), 300-306. PMID: 40814081
9. Oprea, A. D., et al. (2025). Perioperative management of patients taking glucagon-like peptide 1 receptor agonists: Society for Perioperative Assessment and Quality Improvement (SPAQI) multidisciplinary consensus statement. Br J Anaesth, 135(1), 48-78. PMID: 40379536
10. Baig, M. U., et al. (2025). Glucagon-like peptide-1 receptor agonist use and the risk of residual gastric contents and aspiration in patients undergoing GI endoscopy: a systematic review and a meta-analysis. Gastrointest Endosc, 101(4), 762-771.e13. PMID: 39694296
11. Chang, M. G., et al. (2024). A Scoping Review of GLP-1 Receptor Agonists: Are They Associated with Increased Gastric Contents, Regurgitation, and Aspiration Events? J Clin Med, 13(21). PMID: 39518474

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.