Ozempic, Wegovy & Mounjaro: What They Do to Your Digestive System

Informational guide: it does not replace your doctor's assessment and is not a recommendation to start, change or stop a treatment. Always follow the instructions of whoever prescribes it.

Ozempic, Wegovy and Mounjaro have become very popular for diabetes and weight loss, and with them a lot of digestive questions have arrived in clinic: nausea, a feeling that "food won't go down", constipation… and one very important question that often no one has explained: what happens if you take one of these drugs and you are due to have an endoscopy or a sedation. Let's go through it calmly, with the evidence in hand.

1Part 1 of 6

What they are and why they affect digestion

They are drugs that mimic a gut hormone, GLP-1. Under different brand names there are two main molecules: semaglutide (sold as Ozempic for diabetes and as Wegovy for obesity; there is also a tablet, Rybelsus) and tirzepatide (Mounjaro for diabetes and Zepbound for obesity); liraglutide (Victoza/Saxenda) is the older daily version.

They make you eat less through two routes that also explain their side effects: they act on brain areas that control appetite (more fullness, less hunger) and, above all, they slow down how fast the stomach empties, so food stays inside longer and you feel full sooner. ¹² That same braking of the stomach is the root of almost all the digestive effects: it is not a fault of the drug, it is part of how it works.

2Part 2 of 6

The common digestive effects

Digestive symptoms are by far the most common side effects across the whole group: nausea, diarrhoea, vomiting and constipation. In the large trial of semaglutide for obesity (STEP 1), nausea was the most frequent effect (44%) and diarrhoea 31%, but the study itself stresses they were typically mild-to-moderate and transient: only 4.5% stopped treatment because of digestive symptoms. ³

With tirzepatide (Mounjaro/Zepbound) the pattern is the same and very dose-dependent: nausea around 25-33%, diarrhoea 19-23%, constipation 12-17% and vomiting 8-12%, appearing mainly during the dose build-up. ⁴ In diabetes the figures are somewhat lower (nausea 12-24%), but just as transient. ⁵ If you notice nausea or some loose stools, it is almost always expected and improves over time; if you develop constant nausea or constipation that does not settle, mention it to your doctor.

3Part 3 of 6

The "slow digestion": delayed gastric emptying

When you say "food won't go down", you are right: these drugs slow the emptying of the stomach, and the effect is significant. With semaglutide, in a study using a scan, 4 hours after eating there was still 37% of the meal left in the stomach (with placebo, none), and the time to empty half went from about 118 to 171 minutes. ⁶

Two reassuring points. First, with the weekly forms the braking is greatest at the start and fades over time (the body gets used to it), although some background slowing usually remains. Second, this is a functional and reversible effect —the stomach is not "broken"—, different from chronic gastroparesis. ⁷

Key idea: the "slow digestion" of Ozempic is its own mechanism (that is why it curbs appetite), not damage to the stomach, and it tends to fade over time.

4Part 4 of 6

How to cope with the symptoms

The good news is that almost everything can be softened. The most effective measure, by far, is the one your doctor already builds into the prescription: increasing the dose very slowly ("start low and go slow"). Skipping that build-up is the most common cause of severe nausea and vomiting, so never bring it forward on your own. ⁸

Evidence-based tips for nausea

Eat slowly and in small portions, and stop as soon as you feel full.
Choose low-fat, easy-to-digest food; avoid fried food, rich sauces, spicy dishes and large amounts of sweets.
Don't lie down right after eating.
Drink fluids in small sips throughout the day so you don't get dehydrated.
For constipation: fibre, plenty of fluids and physical activity.

These are the measures set out in expert consensus statements; over-the-counter anti-nausea drugs have little evidence here and it is usually better to adjust the dose with your doctor. ⁸

5Part 5 of 6

Speak up before an endoscopy or sedation

This is, to me, the most important part of the article. Because the stomach empties more slowly, food or liquid can remain inside even if you have fasted. If you are sedated or anaesthetised at that point, that content can come up and pass into the lungs: this is aspiration, a potentially serious complication. That is why the team (endoscopist and anaesthetist) needs to know you take the drug. ¹

It is not an exaggeration: in gastroscopies, retained food was found in about 1 in 4 people taking semaglutide (24%) versus 1 in 20 (5%) of those not taking it. ⁹ Another study, looking at the stomach with ultrasound before anaesthesia, found content in 56% of users versus 19%. ¹⁰ Pooling all the studies together, a non-empty stomach is of the order of 5-6 times more common with these drugs. ¹¹

What the guidelines say (and why not to panic)

Retained food is common, but an actual aspiration is rare —precisely because precautions are taken. Anaesthetists (2023 ASA guidance) propose, as a prudent rule, holding the weekly drugs one week before and the daily ones on the same day. The gastroenterology guidance (AGA 2024) is more individualised: in people without symptoms who have met the fast, the endoscopy is usually not postponed, and as an alternative to stopping the drug a clear-liquid diet the day before can be used, checking the stomach with ultrasound if there is any doubt. ¹²¹³

Key idea: don't stop it on your own. Tell the team doing the procedure and let them decide (clear-liquid diet, waiting or precautions); if you take it for diabetes, simply stopping it can destabilise your blood sugar.

6Part 6 of 6

Serious risks (uncommon)

Beyond the usual symptoms, there are a few serious digestive risks worth knowing about without alarm: they are uncommon, but recognised.

Gallstones and gallbladder problems: the best-documented serious digestive risk. A meta-analysis of 76 trials put it at 37% more biliary disease overall (RR 1.37); the risk rises a little more at high doses (around 56% more) and reaches more than double when used for weight loss with marked weight loss. Part of this is that these drugs also empty the gallbladder more slowly.¹⁴
Pancreatitis: it appears as a warning on the drug label; the evidence on whether the risk actually increases is mixed. The warning sign is severe, continuous pain in the pit of the stomach that spreads to the back: if it appears, do not take the next dose and seek help.¹⁵¹⁶
Bowel obstruction / ileus: the drug regulator (FDA) added ileus (a halt in gut transit) to the label; it is an uncommon report, but a real one.¹⁵¹⁶
Dehydration from severe vomiting or diarrhoea, which in rare cases has harmed the kidney: keep up your fluids and seek help if you cannot keep liquids down.¹⁶

Myths and facts

These are the four misunderstandings I see most with these drugs, and what the evidence really says.

Myth: "Ozempic paralyses your stomach forever"

Fact: the slowing is not damage, it is the drug's mechanism; with the weekly forms it fades over time and generally reverses when adjusted or stopped. Persistent gastroparesis is uncommon.⁷

Myth: "You can't have an endoscopy on Ozempic"

Fact: you can. The gastroenterology guidance recommends an individualised approach: without symptoms of retention, the procedure is usually not postponed, and sometimes a clear-liquid diet the day before is enough. It is not an absolute contraindication —but always speak up.¹²

Myth: "This is only for diabetics"

Fact: they are also approved for obesity: semaglutide as Wegovy and tirzepatide as Zepbound, not only Ozempic or Mounjaro for diabetes.¹⁷

Myth: "It's a risk-free shortcut"

Fact: they have real digestive effects and some uncommon serious risks (gallstones, signs of gastroparesis, obstruction or pancreatitis). The absolute risk is low, but it justifies using them under medical supervision, not on your own.¹⁵

Warning signs: when not to wait

Mild symptoms are expected, but do not take the next dose and seek medical care if you develop:¹⁵¹⁶

Severe, continuous pain in the pit of the stomach that spreads to the back (possible pancreatitis).
Severe pain under the right ribs, fever or yellowing of the skin and eyes (possible gallbladder problem).
Vomiting that stops you keeping fluids down, marked bloating, not passing gas or stool with cramping pain (possible bowel obstruction).
Signs of dehydration: dizziness on standing, passing very little urine, a very dry mouth.
And remember: before any endoscopy, surgery or sedation, speak up about taking the drug.

My approach in clinic

I see more and more people who take one of these drugs and arrive with digestive questions or worried by an alarming headline. My job is usually to put things in perspective: to tell the expected nausea of a dose increase from a symptom that needs looking into, to give concrete measures and, very importantly, to review safety before an endoscopy: which drug you take, whether it is daily or weekly, when the last dose was and what preparation makes sense.

If you take Ozempic, Wegovy or Mounjaro and have digestive symptoms, or you are going to have a gastroscopy or colonoscopy, we can plan it well and calmly.

Discuss my case

In-person or online consultation, and planning your endoscopy if you take a GLP-1 drug.

A personal note

These drugs have transformed the treatment of diabetes and obesity, and used well they are very useful. But as a gastroenterologist and endoscopist I see the other side: digestive effects that need managing and a safety precaution —the slow-emptying stomach before a sedation— that often no one has explained to the patient. My aim with this guide is for you to know about it and to reach your doctor well informed.

Dr. Pedro de María in the operating theatre, focused on advanced endoscopy

FAQ: quick questions about GLP-1 drugs and digestion

Why do Ozempic and similar drugs cause nausea and "slow digestion"?

Because one of the ways Ozempic, Wegovy and Mounjaro work is by slowing down how fast the stomach empties: food stays inside longer, which curbs appetite but also causes nausea, fullness or vomiting. It is the most common side effect (nausea affects around 44% of people on the high dose of semaglutide) and it is dose-dependent: it appears mainly when starting and when moving up a dose, is usually mild and temporary, and eases a lot when the dose is increased slowly. ³

Do I have to speak up before an endoscopy or surgery if I take Ozempic, Wegovy or Mounjaro?

Yes, always. Because these drugs empty the stomach more slowly, food or liquid can remain inside even if you have fasted, and that raises the risk of that content passing into the lungs during sedation (aspiration). Tell your doctor, your endoscopist and the anaesthetist in advance, say the name of the drug and whether it is daily or weekly, and do not stop it on your own: the team will decide whether a clear-liquid diet the day before, waiting, or extra precautions are needed. This matters especially if you take it for diabetes, because simply stopping it can destabilise your blood sugar. ¹³

Does Ozempic paralyse the stomach forever?

No. The slowed emptying is not damage to the stomach but the drug's own mechanism (that is why it curbs appetite). Also, with the long-acting weekly forms the effect tends to fade over time, and it generally reverses when the treatment is adjusted or stopped. Persistent gastroparesis (a stomach that empties very slowly) is uncommon. Even so, that slowing is the reason it has to be taken into account before an endoscopy or sedation. ⁷

How do I reduce the nausea from Ozempic or Wegovy?

The most effective measure is to increase the dose slowly (never skip the dose-escalation schedule). It also helps to eat small portions slowly, stop when you feel full, choose low-fat, easy-to-digest food, not lie down right after eating and sip fluids in small amounts. For constipation, make sure you get fibre, plenty of fluids and physical activity. If the nausea or vomiting is severe or you cannot keep fluids down, check with your doctor before the next dose. ⁸

References (clickable)

Jalleh RJ, Rayner CK, Hausken T, et al. Gastrointestinal effects of GLP-1 receptor agonists: mechanisms, management, and future directions. Lancet Gastroenterol Hepatol (2024). PMID: 39096914 (opens in a new tab)
Moiz A, Filion KB, Tsoukas MA, et al. Mechanisms of GLP-1 Receptor Agonist-Induced Weight Loss: A Review of Central and Peripheral Pathways. Am J Med (2025). PMID: 39892489 (opens in a new tab)
Wilding JPH, Batterham RL, Calanna S, et al. (STEP 1). Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med (2021). PMID: 33567185 (opens in a new tab)
Jastreboff AM, Aronne LJ, Ahmad NN, et al. (SURMOUNT-1). Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med (2022). PMID: 35658024 (opens in a new tab)
Patel H, et al. Gastrointestinal adverse events and weight reduction in people with type 2 diabetes treated with tirzepatide in the SURPASS trials. Diabetes Obes Metab (2024). PMID: 37853960 (opens in a new tab)
Jensterle M, et al. Semaglutide delays 4-hour gastric emptying in women with polycystic ovary syndrome and obesity. Diabetes Obes Metab (2023). PMID: 36511825 (opens in a new tab)
Jalleh RJ, Plummer MP, Marathe CS, et al. Clinical Consequences of Delayed Gastric Emptying With GLP-1 Receptor Agonists and Tirzepatide. J Clin Endocrinol Metab (2024). PMID: 39418085 (opens in a new tab)
Gorgojo-Martínez JJ, Mezquita-Raya P, et al. Clinical Recommendations to Manage Gastrointestinal Adverse Events in Patients Treated with GLP-1 Receptor Agonists: A Multidisciplinary Expert Consensus. J Clin Med (2023). PMID: 36614945 (opens in a new tab)
Silveira SQ, da Silva LM, de Campos Vieira Abib A, et al. Relationship between perioperative semaglutide use and residual gastric content: A retrospective analysis of patients undergoing elective upper endoscopy. J Clin Anesth (2023;87:111091). PMID: 36870274 (opens in a new tab)
Sen S, Potnuru PP, Hernandez N, et al. Glucagon-Like Peptide-1 Receptor Agonist Use and Residual Gastric Content Before Anesthesia. JAMA Surg (2024). PMID: 38446466 (opens in a new tab)
Tarar ZI, Farooq U, Chaudhry A, et al. Evidence Report on the Safety of Gastrointestinal Endoscopy in Patients on GLP-1 Receptor Agonists: A Systematic Review and Meta-Analysis. Diagnostics (Basel) (2025). PMID: 40150111 (opens in a new tab)
Hashash JG, Thompson CC, Wang AY. AGA Rapid Clinical Practice Update on the Management of Patients Taking GLP-1 Receptor Agonists Prior to Endoscopy: Communication. Clin Gastroenterol Hepatol (2024). PMID: 37944573 (opens in a new tab)
Kindel TL, Wang AY, Wadhwa A, et al. Multisociety Clinical Practice Guidance for the Safe Use of GLP-1 Receptor Agonists in the Perioperative Period. Surg Endosc (2024). PMID: 39370500 (opens in a new tab)
He L, Wang J, Ping F, et al. Association of GLP-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). PMID: 35344001 (opens in a new tab)
Sodhi M, Rezaeianzadeh R, Kezouh A, Etminan M. Risk of Gastrointestinal Adverse Events Associated With GLP-1 Receptor Agonists for Weight Loss. JAMA (2023). PMID: 37796527 (opens in a new tab)
Ozempic (semaglutide) — FDA Prescribing Information (pancreatitis, ileus/intestinal obstruction, acute kidney injury from dehydration, delayed gastric emptying). DailyMed, U.S. National Library of Medicine. dailymed.nlm.nih.gov (opens in a new tab)
Wegovy (semaglutide) — FDA Prescribing Information (indication in obesity; delayed gastric emptying). DailyMed, U.S. National Library of Medicine. dailymed.nlm.nih.gov (opens in a new tab)

Ozempic, Wegovy & Mounjaro: What They Do to Your Digestive System | 2026 Guide

Ozempic, Wegovy and Mounjaro: what they do to your digestive system