From Clinic to Recovery · First Edition
Chapter 23 — GLP-1 and GIP/GLP-1 Receptor Agonists: Weight-Loss and Diabetes Injections
Dr. Tamer Rushdy Elalfy · 11 min read
In this chapter
Weekly injections such as semaglutide and tirzepatide, and related daily injections and tablets, have become some of the most widely used medicines in the world, for diabetes and for weight loss. Many surgical patients take them, sometimes bought online or abroad, and do not always mention them because they do not think of them as “medicines.” These drugs slow stomach emptying, so food can remain in the stomach despite normal fasting, raising concern about aspiration during anesthesia. Guidance has changed quickly and still differs between societies. This chapter explains how to identify these patients, how to apply current guidance, and how to counsel them about other surgical effects of the medicines.
Learning objectives After reading this chapter you should be able to:
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Table 23.1. GLP-1 and GIP/GLP-1 receptor agonists and surgery at a glance.
| At a glance | |
|---|---|
| Examples | Semaglutide, tirzepatide, liraglutide, dulaglutide, and others; injections or tablets |
| Main surgical concern | Slowed stomach emptying: food may remain in the stomach despite normal fasting |
| Current guidance | Most patients continue the medicine; higher-risk patients may need a 24-hour liquid diet and an adapted anesthesia plan |
| Other issues | Gallstones, nausea and dehydration, low blood glucose with insulin or sulfonylureas, contraception with tirzepatide |
| The key counseling message | “Tell us about your injection, its dose, and your last dose. Do not stop it on your own; we will give you a clear plan.” |
STEP 1 Understanding the medicines and the guidance
23.1 Why these medicines matter for surgery
GLP-1 receptor agonists and dual GIP/GLP-1 receptor agonists reduce appetite and slow stomach emptying. This effect is strongest when the medicine is started or the dose is increased, and in patients who have nausea, vomiting, bloating, or early fullness. Retained food in the stomach at the start of anesthesia increases the risk of aspiration into the lungs. The medicines also affect other aspects of surgical care: they are associated with gallbladder and biliary disease [1], they can cause dehydration through nausea and reduced intake, and they increase the risk of low glucose when combined with insulin or sulfonylureas.
23.2 What current guidance says
Three major guidance documents agree that most patients can continue these medicines before elective surgery, but differ in how they manage the risk of retained stomach contents (Table 23.2). Each hospital should adopt one approach, agreed between anesthesia, surgery, and endocrinology, and apply it consistently.
Table 23.2. Current guidance on GLP-1 and GIP/GLP-1 receptor agonists before elective surgery.
| Guidance | Main recommendations |
|---|---|
| Multisociety clinical practice guidance, 2024 [2] | Most patients continue the medicine. Patients at higher risk (dose escalation, higher doses, gastrointestinal symptoms) may follow a liquid diet for 24 hours before surgery, or have the anesthetic plan adjusted. |
| UK multidisciplinary consensus, 2025 [3] | Continue the medicine, with individual risk assessment and an anesthetic plan for patients at higher risk. |
| SPAQI multidisciplinary consensus, 2025 [4] | Continue the medicine, but extend the preoperative fast, including 24 hours without solid food for patients without significant symptoms. |
[Figure — diagram omitted in this text edition; see the figure caption below and the Word chapter file for the image]
Figure 23.1. Assessing patients taking GLP-1 or GIP/GLP-1 receptor agonists before surgery.
23.3 Asking the right questions
Script: asking about weight-loss and diabetes injections “Do you take any weekly or daily injection, or a tablet, for weight loss or diabetes? Some people buy these online or abroad. Please tell us about any.” “What is the name and dose? When did you take the last dose? Did you start it, or increase the dose, in the last few weeks?” “In the last few days, have you had nausea, vomiting, bloating, or felt full quickly?” “Please do not stop or change it on your own. We will give you a clear plan for your operation.” |
Caution: products bought online or abroad Some patients use products bought online, from compounding sources, or abroad, and the dose or content may be uncertain. Record the source, ask to see the pen or packaging, and treat the patient as higher risk if the dose or timing is unclear. |
23.4 Other surgical issues
- Gallstones. These medicines are associated with an increased risk of gallbladder and biliary disease [1]; consider gallstones in a patient with upper abdominal pain (Chapter 4).
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Nutrition and muscle. Rapid weight loss can reduce muscle and protein stores. Before major surgery, check intake and encourage protein.
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Low glucose. In patients also taking insulin or sulfonylureas, reduced intake around surgery increases the risk of hypoglycemia (Chapter 18).
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Contraception. Tirzepatide can reduce the effectiveness of oral contraceptive pills; women should use an additional method for 4 weeks after starting and after each dose increase, according to the product information.
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Pregnancy. These medicines are stopped before a planned pregnancy, according to the product information and the prescriber’s advice.
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After bariatric surgery. They may be used as part of a team plan for weight regain (Chapter 13).
STEP 2 Preparation, recovery, and Ramadan
23.5 Before and after surgery
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Plan. Record the medicine details and the anesthetic plan in the notes, and tell the anesthesia team in advance.
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Diet before surgery. Follow the hospital protocol: for many patients, a clear liquid diet for 24 hours before surgery; standard fasting rules still apply on the day (Chapter 2).
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Day of surgery. Report any nausea, vomiting, or bloating on arrival.
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After surgery. Nausea may be more common. Restart the medicine when eating and drinking normally. If several doses have been missed, the prescriber may restart at a lower dose to avoid nausea.
23.6 Ramadan
Many people take these medicines while fasting, but nausea and reduced fluid intake increase the risk of dehydration. Patients should not fast while recovering from surgery, and those who wish to fast afterward should plan with their prescriber [5].
STEP 3 Questions patients ask
“Do I need to stop my weight-loss injection before surgery?”
Usually not. Most current guidance advises continuing it, with a liquid diet the day before for some people [2, 3]. Follow the plan we give you.
“Why does it matter for the anesthetic?”
These medicines slow how fast your stomach empties. Food can stay in your stomach even after normal fasting, which can be dangerous under anesthesia.
“Why a liquid diet the day before?”
Liquids leave the stomach faster than solid food, so your stomach is more likely to be empty for the operation.
“I bought my injection online. Does that matter?”
Please tell us. We need to know exactly what you are taking and when.
“Can the injection cause gallstones?”
It can increase the chance of gallbladder problems [1]. Tell us if you have pain in the upper right side of your tummy.
“When can I restart it after the operation?”
When you are eating and drinking normally. If you missed several doses, your doctor may restart a lower dose.
“I take tirzepatide and the pill. Is that a problem?”
Tirzepatide can make the pill less reliable. Use an extra method, such as condoms, for 4 weeks after starting and after each dose increase.
STEP 4 Risks, warning signs, and consent
23.7 Additional risks
Table 23.3. Additional risks for patients taking GLP-1 or GIP/GLP-1 receptor agonists. Square brackets mark figures to replace with unit data.
| Band | Risk | Typical frequency | Example wording |
|---|---|---|---|
| Common | Nausea after surgery | [unit data] | “Feeling sick may be more common after the operation.” |
| Less common | Postponed operation because of food in the stomach | [unit data] | “If your stomach is not empty, we may need to delay the operation for your safety.” |
| Less common | Low blood glucose with insulin or sulfonylureas | [unit data] | “We will check your sugar often.” |
| Rare but serious | Aspiration of stomach contents into the lungs | [unit data] | “Rarely, food from the stomach enters the lungs. Our plan is designed to prevent this.” |
23.8 Checklist
Before surgery ☐ Asked specifically about weight-loss and diabetes injections and tablets, including products bought online or abroad. ☐ Name, dose, frequency, last dose, recent dose changes, and symptoms recorded. ☐ Risk assessed and anesthesia team informed; plan follows the hospital protocol. ☐ Liquid diet or fasting instructions given in writing. ☐ Hypoglycemia plan for patients on insulin or sulfonylureas. ☐ Restart plan and contraception advice given where relevant. |
23.9 Warning signs
Table 23.4. Green, amber, and red warning signs for patients taking GLP-1 or GIP/GLP-1 receptor agonists.
| Level | Signs | What to do |
|---|---|---|
| Green | Mild nausea for a day or two after restarting | Expected. Eat small meals and drink often. |
| Amber | Nausea or vomiting that stops you drinking for 12 hours Upper abdominal pain after fatty meals | Call your doctor or the clinic the same day. |
| Red | Repeated vomiting, dizziness, or very little urine Severe abdominal pain, especially spreading to the back Yellow eyes or skin Low sugar that does not recover with treatment | Go to the emergency department now. |
Key points
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STEP 5 Patient education guide
The following pages may be photocopied and given to patients. Complete the plan with the patient, and add your unit’s name, phone numbers, and review date before use.
PATIENT GUIDE Weight-Loss and Diabetes Injections and Your Operation For example semaglutide, tirzepatide, liraglutide, or dulaglutide. |
Why this matters
These medicines slow down how fast your stomach empties. Food can stay in your stomach even after normal fasting. Under anesthesia, this can be dangerous. A simple plan keeps you safe.
My plan
| Details | |
|---|---|
| My medicine and dose | |
| How often | ☐ Weekly ☐ Daily ☐ Tablet |
| Last dose before surgery | Date: ________ |
| Day before surgery | ☐ Usual food ☐ Liquids only from: ________ |
| Restart | When eating and drinking normally, on: ________ |
Before your operation
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Do not stop or change your medicine on your own.
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Tell us if you bought it online or abroad.
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If you are on a liquid diet the day before, take only clear liquids such as water, clear juice without pulp, clear soup, and jelly, as told.
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Tell us on arrival if you feel sick, have vomited, or feel bloated.
After your operation
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You may feel sick for a day or two. Eat small meals and drink often.
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Restart your medicine when you are eating and drinking normally.
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If you take tirzepatide and the contraceptive pill: use an extra method for 4 weeks after starting and after each dose increase.
Warning signs: when to get help
| Level | What you notice | What to do |
|---|---|---|
| GREEN | Mild nausea for a day or two | Eat small meals and drink often. |
| AMBER | Cannot drink for 12 hours because of nausea; pain in the upper right tummy after meals | Call your doctor or us today. |
| RED | Repeated vomiting; dizzy with little urine; severe tummy pain; yellow eyes or skin; low sugar that will not come up | Go to the emergency department now. |
My contacts Surgical team: ______________________ Prescriber: ______________________ Out of hours: ______________________ [Unit name] [Guide version and review date] |
References
1. He L, Wang J, Ping F, et al. Association of glucagon-like peptide-1 receptor agonist use with risk of gallbladder and biliary diseases: a systematic review and meta-analysis of randomized clinical trials. JAMA Intern Med. 2022;182(5):513-519.
2. Kindel TL, Wang AY, Wadhwa A, 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;20(12):1183-1186. doi:10.1016/j.soard.2024.08.033
3. El-Boghdadly K, Dhesi J, Fabb P, et al. 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. Anaesthesia. 2025;80(4):412-424. doi:10.1111/anae.16541
4. Oprea AD, Ostapenko LJ, Sweitzer B, et al. 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. 2025;135(1):48-78. doi:10.1016/j.bja.2025.04.001
5. Hassanein M, Afandi B, Yakoob Ahmedani M, et al. Diabetes and Ramadan: practical guidelines 2021. Diabetes Res Clin Pract. 2022;185:109185.
Note: references are numbered within this chapter for the pilot. Items marked in square brackets are collected in the Author Fill-in and Verification Log.