What the labels say about stomach emptying
- Ozempic® and Rybelsus® (semaglutide): a delay of early post-meal gastric emptying, described as a minor delay, which slows how quickly glucose from a meal reaches the blood [1][7].
- Wegovy® (semaglutide): semaglutide delays gastric emptying. The Ozempic® label adds that one separate study found no apparent effect on the rate of gastric emptying with semaglutide 2.4 mg [1][2].
- Mounjaro® and Zepbound® (tirzepatide): the slowing is strongest after the very first dose and fades as treatment continues. After a first 5 mg dose, the peak level of a test medicine (acetaminophen) fell by 55% and came an hour later; at week 6 on 15 mg there was no meaningful effect [3][4].
- Foundayo™ (orforglipron): also largest after the first dose and diminishing over time, with a 28% fall in the acetaminophen peak after the first dose [6].
- Saxenda® (liraglutide): liraglutide delays gastric emptying, with an equivalent effect at 1.8 mg and 3 mg [5].
Is gastroparesis listed as a side effect?
Not in the US labels. There, the word gastroparesis appears only in the warnings and patient information, as a condition people may already have, and not among the adverse reactions in section 6.1 (clinical trials) or 6.2 (post-marketing reports) of any label reviewed here. What section 6.2 does list are post-marketing reports of ileus (the bowel stopping moving), intestinal obstruction and severe constipation including fecal impaction, from a population of uncertain size, so their frequency and cause cannot be reliably established [1][2][3][4].
Other regulators word it differently. The European package leaflets for semaglutide, tirzepatide, liraglutide and dulaglutide list a delay in the emptying of the stomach as an uncommon side effect, meaning up to 1 in 100 people [8][9]. The Canadian Zepbound® monograph, revised in June 2026, says events related to impaired gastric emptying, including severe gastroparesis, have been reported, and asks prescribers to monitor people who develop severe stomach symptoms; the Canadian Mounjaro® monograph carries the same sentence [10].
The severe stomach reactions warning
Each US label has a warning titled severe gastrointestinal adverse reactions, saying use has been associated with stomach reactions that are sometimes severe, and that such reactions have also been reported after approval with GLP-1 medicines [1][4].
The trial rates differ by product: Wegovy® injection 4.1% versus 0.9% on placebo, Wegovy® tablets 2% versus 0%; Saxenda® 4.8% versus 1.4%; Zepbound® 1.7% to 3.1% across doses versus 1%; Foundayo™ about 3% versus 1%; Mounjaro® 0.4% to 1.3% versus 0.9%; Ozempic® 0.4% and 0.8% versus 0%; Rybelsus® 0.6% and 2% versus 0.3% [1][2][3][4][5][6][7].
What studies have measured
How much slowing? A 2024 systematic review and meta-analysis in the American Journal of Gastroenterology pooled 15 studies. On gastric emptying scintigraphy, a scan that follows a solid test meal, the time for half the meal to leave the stomach averaged about 138 minutes on GLP-1 medicines against 95 minutes on placebo, a difference of roughly 36 minutes. Tests based on acetaminophen absorption, which mainly reflect liquids, showed no significant delay, and the type of medicine or length of treatment did not change the result [11].
Diagnosed gastroparesis in trials: the 2025 Gastroenterology meta-analysis of 55 randomised placebo-controlled trials found that GLP-1 medicines probably had little or no effect on gastroparesis, while they did increase gallstones and probably reflux [12].
In everyday use: a 2023 JAMA research letter based on US insurance claims compared new users of semaglutide or liraglutide for weight loss with users of bupropion-naltrexone. GLP-1 users had a higher rate of gastroparesis (hazard ratio 3.67, confidence interval 1.15 to 11.9). Gastroparesis was defined by a billing code or a prescription for a motility medicine, numbers were small, and a claims study cannot show cause [13].
Expected slowing or gastroparesis?
The two are easy to mix up because NIDDK calls gastroparesis “delayed gastric emptying” too. The difference is in what is being described: a predictable effect of the medicine, or a disorder diagnosed after tests.
| Question | Slowing described in the labels | Gastroparesis as NIDDK describes it |
|---|---|---|
| What it is | An intended action of the medicine that also slows how fast glucose from a meal enters the blood [1][3] | A disorder in which stomach muscles work poorly or not at all, without a blockage [14] |
| How it changes over time | For tirzepatide and orforglipron, largest after the first dose and fading with later doses [3][6] | A disorder whose complications can include dehydration, malnutrition and unplanned weight loss [14] |
| How it is found | Measured in pharmacology studies, not diagnosed in the individual [3][11] | History, examination, tests to rule out a blockage, and a stomach-emptying scan, breath test or capsule [14] |
| Who is more likely to have it | Anyone taking the medicine | People with diabetes, after surgery on the stomach or nearby organs, or after radiation to that area [14] |
If you already have gastroparesis
Each US label advises against the medicine for people whose gastroparesis is severe. In the Ozempic® and Saxenda® Medication Guides, a stomach that empties slowly (gastroparesis) or trouble digesting food is on the list of conditions to mention before the first dose [1][5]. The European semaglutide information adds that people with gastroparesis may have more serious or severe stomach side effects, and the European Mounjaro® information says tirzepatide has not been studied in severe gastrointestinal disease and should be used with caution [8][9].
The labels do not set out a separate plan for milder or suspected gastroparesis. Whether a GLP-1 medicine is suitable in that situation is a judgement for your prescriber, ideally with the full history of your symptoms in front of them.
Other causes of similar symptoms
NIDDK notes that true gastroparesis is uncommon, yet symptoms like it occur in about 1 in 4 US adults [14]. Its list of symptoms overlaps heavily with ordinary GLP-1 reactions: feeling full soon after starting a meal or long after finishing it, nausea, vomiting, bloating, belching, upper abdominal pain, heartburn and poor appetite.
Other medicines can also slow emptying or worsen these symptoms, according to NIDDK: opioid pain medicines, some antidepressants, some anticholinergics, some overactive bladder medicines and pramlintide [14]. A blockage has to be ruled out too, which is one reason the labels’ reports of ileus and obstruction matter.
What general guidance says helps
- For people diagnosed with gastroparesis, NIDDK says a doctor may recommend foods and drinks low in fat and fibre, several small meals instead of a few large ones, and soft, well-cooked food, and may suggest avoiding fizzy drinks, alcohol and food that is hard to chew [15]. This advice was written for the diagnosed condition; whether it suits you is a question for your clinician or a dietitian.
- Fluids: the Ozempic®, Wegovy® and Saxenda® Medication Guides say drinking fluids helps lower the chance of dehydration when nausea, vomiting or diarrhea occur [1][2][5].
- Medicine list: NIDDK asks you to tell your doctor about all prescription and over-the-counter medicines and supplements, and the GLP-1 labels say slower emptying can change how other tablets are absorbed [3][14].
Why slower emptying matters elsewhere
- Oral medicines: the labels warn that delayed emptying can change how other tablets are absorbed. The Wegovy® label reports a 33% rise in levothyroxine exposure with the semaglutide tablet, and the tirzepatide labels give instructions for birth control pills during the first weeks and after each dose increase [2][3].
- Anesthesia and sedation: there are rare reports of food or liquid entering the lungs during procedures in people on GLP-1 medicines who had food left in the stomach despite fasting. The labels ask you to tell every provider about the medicine before a planned procedure [1][4].
A record that shows the pattern
Slow emptying is usually described through symptoms: feeling full after a few bites, fullness that lasts for hours, vomiting food eaten long before, bloating. Noting these with the time of the meal, the day of the dose and any dose change gives your clinician something concrete to judge.
Ozempic®, Wegovy®, Rybelsus®, Saxenda® and Victoza® are registered trademarks of Novo Nordisk A/S. Mounjaro®, Zepbound® and Trulicity® are registered trademarks of Eli Lilly and Company, and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Intense belly pain that persists, with or without vomiting, sometimes felt in the back | Stop the medicine and phone your provider without delay | Emergency | Labels, pancreatitis warning [1][4] |
| Red blood in vomit or vomit like coffee grounds, sudden sharp stomach pain that does not go away, fainting or trouble breathing | Emergency care | Emergency | NIDDK [14] |
| Vomiting that goes on for more than an hour, or blood sugar that is too high or too low | A doctor right away | Emergency | NIDDK [14] |
| Severe constipation, a swollen belly, or being unable to pass stool or gas | Your provider the same day | Today | Labels, ileus and obstruction reports [1][3] |
| Repeated vomiting or diarrhea with signs of dehydration, such as extreme thirst, little or dark urine or light-headedness | Your provider promptly | Today | NIDDK [14]; labels, fluid loss warning [1][4] |
| Feeling full after a few bites for weeks, losing weight without trying, or feeling weak all the time | Book a visit and bring your notes | At your next appointment | NIDDK, malnutrition signs [14] |
