Anyone booking a colonoscopy or an elective operation now gets asked whether they are taking one of these drugs. The reason is delayed gastric emptying and what it might mean under sedation. The advice attached to that question was rewritten in 2024, and the earlier version is still the one most often repeated.
What the 2023 guidance said
In June 2023 the American Society of Anesthesiologists issued consensus-based guidance recommending that these drugs be withheld according to their dosing schedule: daily agents on the day of the procedure, weekly agents for one week beforehand.[1] It was a single rule applied to everyone on the class, and it spread quickly through pre-op instructions.
That mattered more than it might sound. A week off a weekly drug is a missed dose, and a gap long enough to disturb a dose schedule has consequences of its own.
What replaced it
In October 2024 a multisociety document took a different position. Five bodies approved it. They were the American Gastroenterological Association, the American Society for Metabolic and Bariatric Surgery, the American Society of Anesthesiologists, the International Society of Perioperative Care of Patients with Obesity, and the Society of American Gastrointestinal and Endoscopic Surgeons. Therapy “may be continued pre-operatively in patients without elevated-risk of delayed gastric emptying and aspiration”.[2]
Elevated risk is defined rather than left to instinct. The document names the escalation phase rather than maintenance, a higher dose, weekly rather than daily dosing, the presence of gastrointestinal symptoms, and medical conditions that delay gastric emptying independently of the drug.[2] Where risk is elevated, it says withholding should be balanced against the surgical and medical risk of doing so. Two of those five factors are about where a person sits on the dose ladder, which makes the timing of a procedure relative to a dose increase part of the question.
The mitigations it offers are not all about stopping the drug. A preoperative liquid diet for at least 24 hours is one. Point-of-care gastric ultrasound is another, where a department has it. And where retained contents are suspected or confirmed on the day, it asks clinicians to consider rapid sequence induction for tracheal intubation.[2] The document also describes itself as guidance rather than an evidence-based guideline, which is an unusual thing to say about your own paper and an honest one.
The labels say considerably less
Both manufacturers added a warning on this subject, and both stop short of a recommendation. The Wegovy and Zepbound labels describe rare postmarketing reports of pulmonary aspiration in patients undergoing elective procedures under general anesthesia or deep sedation who had residual gastric contents despite reported adherence to preoperative fasting.[3][4]
Then comes the sentence worth quoting. Available data are insufficient to inform recommendations to mitigate the risk, including whether modifying preoperative fasting or temporarily discontinuing the drug would reduce the incidence of retained gastric contents.[3][4]The single instruction either label gives the patient is to tell the care team about any planned surgery or procedure.
What the measurements actually show
A cross-sectional study used gastric ultrasound on 124 fasted adults before elective procedures. Increased residual gastric content was present in 56% of those taking a weekly GLP-1 receptor agonist, against 19% of those not taking one, an adjusted prevalence ratio of 2.48 (95% CI 1.23 to 4.97). Duration of drug interruption showed no association with residual content, at an adjusted odds ratio of 0.86 (95% CI 0.65 to 1.14).[5]
A meta-analysis reached a smaller-sounding number by a different instrument. Across five scintigraphy studies covering 247 people, gastric emptying half-time was delayed by a pooled 36.0 minutes (95% CI 17.0 to 55.0). Ten studies using the acetaminophen absorption test, which reflects liquid emptying, found no significant delay at all.[6] The authors argued that a delay of that magnitude is small relative to standard fasting periods.
Both results can be true. Average emptying can shift by half an hour while a minority of individuals arrive with a stomach that is not empty, and it is the minority that an anesthesiologist is planning around.
Does a week off fix it
This is where the 2023 rule looks weakest. A prospective study scanned 93 fasted adults before elective surgery, comparing people who had stopped a weekly GLP-1 for at least 7 days against people not taking one. Increased residual gastric content was found in 42% of those who had held the drug for a week, against 24% of controls — an adjusted prevalence ratio of 1.65 (95% CI 0.7 to 3.7).[7]
The difference did not reach statistical significance and the authors say plainly that the study was underpowered. What it does not show is the thing the blanket rule assumed: that seven days reliably returns the stomach to baseline.
The outcome data have not found the harm
Residual content is a risk factor, not an event. An observational analysis of an electronic health record network propensity-matched surgical patients with type 2 diabetes taking a GLP-1 receptor agonist against those taking metformin, an SGLT2 inhibitor or a DPP-4 inhibitor. Preoperative use was associated with lower 14-day mortality against metformin, 0.98% versus 2.20%, a risk ratio of 0.44 (95% CI 0.31 to 0.64), and with no increased aspiration risk against any comparator class.[8]
That is an observational comparison of people with diabetes, and the authors call for prospective confirmation. It is still the shape of the current picture: a measurable emptying delay, a real minority with retained contents, and no population-level signal of more aspiration.
Why this lands differently on a telehealth prescription
A hospital pre-op questionnaire asks what you take. A compounded vial often arrives labeled by a pharmacy rather than under a brand name, and the dose is a volume rather than a familiar pen click, so the answer is harder to give accurately. Anything the anesthesia team is going to stratify on — molecule, dose, how recently it went up, whether nausea is present — has to be known before it can be reported.
That is one practical argument for buying from a seller that names the pharmacy and states the dose in milligrams, which is recorded in the seller reviews against the criteria in the methodology. The same information matters when comparing compounded tirzepatide sellers on anything other than price.
Whether to hold this drug before a procedure is a decision for the anesthesiologist and the prescribing clinician together, with the procedure and the metabolic need on the table. The useful thing a patient can do is raise it early, and raise it with the specific product and dose named.