The hospital sent me the standard fasting instructions and never mentioned my injection. Do I follow them?

Those instructions assume a stomach clearing at its usual speed, which is the assumption this drug breaks. Ring pre-assessment before the day, give them the product name, the dose, and the date of your last injection, and let them say whether anything about the plan changes. Ask for their answer in writing so nobody has to relitigate it at 7am on a trolley.

My operation got cancelled and rebooked. Do I have to go through all this again?

Yes, and it is the dose that makes it worth repeating rather than the admin. If you stepped up between the two dates, you have moved toward the group teams handle more carefully, since the emptying delay peaks straight after an increase. Give them today's dose and the date it changed, not whatever went on the form last time.

It is a filling under local anaesthetic. Does the dentist really need to know?

The concern in the guidance attaches to sedation and general anaesthesia, because those are what suppress the reflexes protecting the airway. Local anaesthetic on its own does not do that. Mentioning it still costs you nothing, and it matters if the plan changes on the day to include sedation.

GLP-1 and Surgery: What to Tell Your Anaesthetist

What this page establishes

2023 ASA consensus guidance advised holding weekly GLP-1 injections for the week before a procedure and daily doses on the day of the procedure.
The October 2024 multisociety guidance (ASA, AGA, ASMBS, ISPCOP, SAGES) states GLP-1 RAs may be continued preoperatively in patients without elevated risk of delayed gastric emptying and aspiration.
The 2024 guidance recommends patients without significant GLP-1-associated GI symptoms fast from solid food for 24 hours and take clear liquids before a procedure requiring anaesthesia.
Higher-risk features include being in the dose-escalation phase, weekly dosing, higher doses, and current GI symptoms.

Quick answers

The hospital sent me the standard fasting instructions and never mentioned my injection. Do I follow them?
Those instructions assume a stomach clearing at its usual speed, which is the assumption this drug breaks.
Read the full answer
Ring pre-assessment before the day, give them the product name, the dose, and the date of your last injection, and let them say whether anything about the plan changes. Ask for their answer in writing so nobody has to relitigate it at 7am on a trolley.
My operation got cancelled and rebooked. Do I have to go through all this again?
Yes, and it is the dose that makes it worth repeating rather than the admin. If you stepped up between the two dates, you have moved toward the group teams handle more carefully, since the emptying delay peaks straight after an increase.
Read the full answer
Give them today's dose and the date it changed, not whatever went on the form last time.
It is a filling under local anaesthetic. Does the dentist really need to know?
The concern in the guidance attaches to sedation and general anaesthesia, because those are what suppress the reflexes protecting the airway.
Read the full answer
Local anaesthetic on its own does not do that. Mentioning it still costs you nothing, and it matters if the plan changes on the day to include sedation.

Guidance currency. This page tracks the multisociety perioperative guidance on GLP-1 receptor agonists, dated October 2024. Last checked against that guidance on 2026-08-23, and due for re-check every 12 months. Guidance in this area has changed before and a stale version of this page would be worse than no page, so check the date above before relying on it.

If you take semaglutide, tirzepatide or liraglutide and you have any procedure booked that involves anaesthesia or sedation, the single thing that matters is that the anaesthetic team knows. Say it early, say it at the pre-assessment, and say it again on the day. These drugs slow the rate at which the stomach empties, so food can still be sitting there after the standard fasting period has passed. Under general anaesthesia the reflexes that keep stomach contents out of the lungs stop working, and that is what makes residual food a problem. The guidance on what to do about it changed in October 2024, from holding the drug in everyone to a risk-stratified approach. Whether your dose is held, continued or timed differently is a decision for the team looking after you, and this page exists so you know what they are weighing up.

Say this before anything else

The instruction that carries the most weight on this page is also the shortest. Tell every clinician involved in the procedure that you take a GLP-1 receptor agonist, which one, what dose, when you last injected, and whether you have had a dose increase recently. That last detail matters more than people expect, because the gastric-emptying effect is at its largest right after starting and right after each escalation.

Do not assume the information has travelled. A surgeon knowing is not the same as the anaesthetist knowing, and a referral letter listing your medications is not the same as a pre-assessment nurse having flagged it. If nobody has asked, raise it yourself. Ask what they want you to do about doses between now and the procedure, and ask them to write it down. If the procedure is postponed and rebooked, raise it again, because a dose increase in the interval changes the answer.

Contact the team before the day if any of this applies A procedure is booked and you have not yet disclosed that you take a GLP-1. You have had a dose increase in the days before the procedure. You currently have nausea, vomiting, or a sense of food sitting in your stomach. You have been given standard fasting instructions with no mention of the drug. Any of these warrant a phone call to the pre-assessment or anaesthetic team rather than waiting until you arrive.

Why a slowed stomach matters under anaesthesia

Standard preoperative fasting rules exist because an empty stomach cannot be aspirated. The usual intervals, several hours without solids and a shorter window for clear liquids, are built on the assumption that the stomach empties at a normal rate. General anaesthesia and deep sedation abolish the airway reflexes that would otherwise stop stomach contents entering the lungs, so the fasting interval is the only protection in place.

A GLP-1 receptor agonist works partly by slowing that emptying. The same mechanism that makes you feel full for hours after a small meal means solid food can remain in the stomach past the point where the fasting rules assume it has gone. Endoscopists have documented residual solid contents in patients who fasted correctly. That residual volume is the aspiration risk, and it is the entire reason perioperative guidance for this drug class exists.

The delay is not constant. It is largest at initiation and after each dose increase, and it diminishes at a steady dose. Someone six months into maintenance and someone two weeks into a first escalation are not in the same situation, which is what the 2024 guidance is built around.

The 2023 ASA guidance

In June 2023 the American Society of Anesthesiologists issued consensus-based guidance advising that weekly GLP-1 injections be held for the week before a procedure, and daily doses held on the day. It was a blanket recommendation applied across patients, and the ASA was explicit that the evidence behind it was sparse, resting largely on case reports of residual gastric contents and aspiration rather than on trials. That is part of why the position was revisited.

What changed in October 2024

In October 2024 a multisociety group published updated guidance in Clinical Gastroenterology and Hepatology. The societies involved were 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.

The headline change: GLP-1 receptor agonists may be continued before a procedure in patients who do not have an elevated risk of delayed gastric emptying and aspiration. Blanket withholding was replaced by an individual risk assessment. The reasoning is that stopping the drug is not free either, particularly for people with type 2 diabetes whose glycaemic control depends on it, and that most patients on stable maintenance doses do not carry the risk the 2023 advice assumed.

If you find advice online telling you to stop your weekly injection a week before any procedure, check its date. That was the 2023 position. Your team may still choose to hold your dose, and that choice may well be right for you, but it should be a decision made about you rather than a rule applied to everyone.

The 24-hour clear-liquid recommendation

The 2024 guidance pairs continuation with a change to the fasting instructions. For patients without significant GLP-1-associated gastrointestinal symptoms, it recommends fasting from solid food for 24 hours before a procedure requiring anaesthesia, and taking clear liquids during that period.

That is a considerably longer solid-food fast than the standard rule. It gives a slowed stomach extra time to clear, while clear liquids, which empty far faster than solids, keep the patient hydrated. Whether the 24-hour window applies to you is the team's call, and someone with current nausea or vomiting falls outside the group it was written for.

Who counts as higher risk

The 2024 guidance names the features that push someone into the higher-risk group. None is a disqualification from surgery. They make a team more likely to hold a dose, extend the fast, use ultrasound to look at the stomach before induction, or treat the patient as though the stomach is full.

The decision is not yours to make alone Whether to hold, continue or delay a dose around a procedure is the anaesthetic team's decision. Do not stop the drug, and do not keep taking it, on the basis of a guideline you read yourself. Bring the question to them.

Feature	Why it raises risk
Currently in the dose-escalation phase	The gastric-emptying delay is at its largest after each dose increase
Weekly dosing	Drug exposure is continuous across the week rather than clearing daily
Higher doses	Greater effect on gastric motility
Current GI symptoms	Nausea, vomiting or early fullness signal a stomach that is not clearing normally

Endoscopy, dental sedation and anything else with sedation

The risk attaches to the loss of airway reflexes, not to the specialty performing the procedure. Upper endoscopy is the clearest case, both because it involves sedation and because it is where residual gastric contents get seen. A gastroenterologist who finds a stomach full of food will usually abandon the procedure, which costs you the appointment and the preparation.

Dental sedation counts. So does any day-case or outpatient procedure involving sedation, whether or not anyone uses the word anaesthetic. If someone is going to give you something that makes you drowsy or unconscious, they need to know about the drug.

If you have type 2 diabetes

Glucose management around a procedure needs its own plan, and it interacts with the GLP-1 decision. ADA Standards of Care 2026 direct that when a GLP-1 receptor agonist is present, sulfonylureas be discontinued or reduced and insulin doses adjusted to avoid hypoglycaemia, and a prolonged preoperative fast changes that arithmetic again. Holding a GLP-1 is not a neutral act if your diabetes control depends on it, which is the kind of trade-off the 2024 risk-stratified approach exists to let teams weigh. Get your diabetes team involved alongside the anaesthetic team.

Not medical advice

This page describes published guidance from named professional bodies so you know what your team is working from. It is general educational information, not advice about your procedure or your dose. Reviewed against the October 2024 multisociety guidance. Recommendations in this area are actively changing, so treat anything here as a prompt for a conversation rather than an instruction.

The evidence, one row per claim

Claim	Tier	Source
2023 ASA consensus guidance advised holding weekly GLP-1 injections for the week before a procedure and daily doses on the day of the procedure.	established	ASA Consensus-Based Guidance on Preoperative Management of Patients on GLP-1 Receptor Agonists (2023)
The October 2024 multisociety guidance (ASA, AGA, ASMBS, ISPCOP, SAGES) states GLP-1 RAs may be continued preoperatively in patients without elevated risk of delayed gastric emptying and aspiration.	established	Multisociety Clinical Practice Guidance for Safe Use of GLP-1 RAs in the Perioperative Period, Clinical Gastroenterology and Hepatology
The 2024 guidance recommends patients without significant GLP-1-associated GI symptoms fast from solid food for 24 hours and take clear liquids before a procedure requiring anaesthesia.	established	Multisociety perioperative guidance (2024)
Higher-risk features include being in the dose-escalation phase, weekly dosing, higher doses, and current GI symptoms.	established	Multisociety perioperative guidance (2024)
The original 2023 guidance was based on sparse evidence, largely case reports of residual gastric contents and aspiration.	established	ASA 2023 guidance

Questions people ask

Will they cancel if I tell them?

Disclosure is not the thing that cancels procedures. A team weighing your case can continue, lengthen the fast, look at the stomach with ultrasound before induction, or manage you as though the stomach is full. What genuinely costs people their slot is arriving undisclosed, because an endoscopist who finds residual food will usually abandon the procedure there and then.

Sources

Where this comes from

Researched and edited by Thomas Prommer — biohacker, performance athlete, data enthusiast and health coach.

Every number on this page traces to a named source. There are 5 sourced claims below the fold, each with the document it came from.

Sources consulted: ASA Consensus-Based Guidance on Preoperative Management of Patients on GLP-1 Receptor Agonists, Multisociety Clinical Practice Guidance for Safe Use of GLP-1 RAs in the Perioperative Period, Multisociety perioperative guidance, ASA 2023 guidance.

Not clinically reviewed. This page was researched and written against primary regulatory and trial sources, and no clinician has checked it.

Sources last read 2026-08-23.

Keep reading

Educational content, reviewed 2026-08-23. Not medical advice, not a prescription, and not a substitute for a clinician who knows your history. Doses named here are label schedules or doses used in named trials, never a recommendation to you.