Three rows that travel together
Zepbound®’s US label builds its side-effect table from SURMOUNT-1 and SURMOUNT-2, two 72-week placebo-controlled trials in 2,519 adults on Zepbound®; only SURMOUNT-1 tested 5 mg. [1][3] Abdominal distension and flatulence each cleared the table’s entry bar of at least 2% and more frequent than placebo by a narrow margin. [1] Constipation, which the label defines to include hard stools, sits several rows higher. [1]
The EU has not authorised Zepbound®; European product information describes tirzepatide under the Mounjaro® name and classes a bloated stomach and wind as common, and constipation as very common in the weight-management trials. [4]
| Source and row | Zepbound® 5 mg | 10 mg | 15 mg | Placebo |
|---|---|---|---|---|
| Abdominal distension, US Table 1 [1] | 3% | 3% | 4% | 2% |
| Abdominal distension, Canadian Table 2, people (%) [3] | 22 (3.5%) | 32 (3.4%) | 38 (4.0%) | 21 (2.2%) |
| Flatulence, US Table 1 [1] | 3% | 3% | 4% | 2% |
| Flatulence, Canadian Table 2 [3] | 21 (3.3%) | 30 (3.2%) | 38 (4.0%) | 15 (1.6%) |
| Constipation, US Table 1 [1] | 17% | 14% | 11% | 5% |
| Constipation, Canadian Table 2 [3] | 106 (16.8%) | 134 (14.1%) | 102 (10.8%) | 50 (5.2%) |
| EU, tirzepatide sold as Mounjaro® [4] | Bloating and wind: common (up to 1 in 10). Constipation in weight management: very common (more than 1 in 10) |
Reading the gap from placebo
For distension and gas, the difference from placebo is one or two percentage points and edges up slightly at 15 mg. [1][3] Constipation runs the other way: about three times the placebo rate at 5 mg and lower at each higher dose. [1][3] Everyone in the two trials, including the placebo group, received instruction on a reduced-calorie diet and more physical activity, [1] so the placebo figures show how often these complaints appeared among people making the same changes without the medicine.
Neither bloating nor gas appears among the twelve most common side effects in the US Medication Guide, [2] whereas Canada’s patient information names a bloated stomach and gas among possible side effects. [3] For the sleep apnoea trials, at 10 or 15 mg, the US label says reactions resembled the weight trials and prints no separate figures. [1]
Why the belly may swell: three layers
- In the label. Tirzepatide slows stomach emptying, most of all after the first dose, with the effect fading over time. [1] Distension, gas and constipation were all more frequent than on placebo, [1] although the label does not tie any of them to that slowing.
- In reviews, not measured for bloating. A 2025 review of digestive side effects in obesity treatment attributes them mainly to altered gut movement and hormone-driven changes in appetite signalling, and reports such effects in 65% to 84% of people on liraglutide, semaglutide or tirzepatide in trials. [6] It does not single out bloating, so this is a likely route rather than a tested one.
- In general medicine. MedlinePlus explains that gas forms normally as food is digested and can cause bloating and crampy pain, and that adding fibre can bring temporary gas while the body adjusts. [9] The AGA review handles bloating linked to constipation as its own situation, with separate tests and treatment. [7]
Where constipation fits in
Because constipation is the largest of the three rows on Zepbound®, it is often the first thing a clinician will ask about when the belly feels full and tight. A meta-analysis of six randomised trials in people without diabetes found constipation on tirzepatide at a risk ratio of 2.85 compared with placebo. [5] The AGA expert review suggests considering constipation treatment when bloating comes with constipation, and testing for a pelvic floor problem when bloating seems tied to difficult emptying of the bowel. [7]
At the far end, the US label lists severe constipation with faecal impaction, ileus and intestinal obstruction among reports received after approval, without frequencies. [1] Those reports are rare compared with the everyday rows above, but they explain why worsening bloating with no bowel movements needs attention rather than patience.
Other reasons for a swollen belly
MedlinePlus says a swollen abdomen is more often due to overeating than to serious illness. Other causes it lists include swallowed air, gas from high-fibre foods, irritable bowel syndrome, lactose intolerance, premenstrual syndrome, pregnancy, weight gain, uterine fibroids, ovarian cysts, partial bowel blockage and fluid building up in the abdomen, the last being a sign of a serious problem. [8]
For gas, MedlinePlus adds certain medicines such as antibiotics, malabsorption, chewing gum, smoking, fizzy drinks, sweets with sugar substitutes, talking while eating and eating too fast. [9] The AGA review describes how clinicians look for carbohydrate intolerances, bacterial overgrowth in the small intestine and coeliac disease when bloating persists. [7]
What general sources say may help
- Smaller meals; MedlinePlus notes that swelling after a heavy meal settles as the food is digested. [8]
- For swallowed air: avoiding fizzy drinks, chewing gum, hard sweets and straws, and eating slowly. [8]
- For gas: chewing thoroughly, relaxing at meals, cutting back on beans, cabbage, onions and similar foods, avoiding lactose if it troubles you, and a short walk after eating. [9]
- MedlinePlus mentions a low-FODMAP diet for gas; the AGA review prefers that such diets are supervised by a gastroenterology dietitian. [7][9]
- The AGA review advises against probiotics for bloating and distension. [7] Before adding any over-the-counter remedy, ask your pharmacist, because Zepbound® can change how tablets are absorbed. [1]
When bloating is a warning sign
Canada’s patient information describes two Zepbound®-listed conditions in which bloating is central: gastroparesis, with pain, severe nausea and vomiting and long-lasting belching and bloating, and ileus, with bloating, cramping, gas, vomiting, constipation and loss of appetite. For both it tells you to stop Zepbound® and get immediate medical help. [3] The AGA review reserves scans and endoscopy for bloating with alarm features, recent worsening or an abnormal examination, and suggests a stomach emptying test may be considered when nausea and vomiting are also present. [7]
Zepbound® and Mounjaro® are registered trademarks of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Bloating with abdominal pain and cramping, gas, nausea, vomiting, constipation and loss of appetite | Stop Zepbound® and get immediate medical help (possible ileus) | Emergency | Canadian patient information [3] |
| Long-lasting bloating and belching with pain and severe nausea or vomiting | Stop Zepbound® and get immediate medical help (possible gastroparesis) | Emergency | Canadian patient information [3] |
| Severe stomach pain that will not go away, with or without vomiting, sometimes felt in the back | Stop Zepbound® and call your prescriber right away | Emergency | Medication Guide [2] |
| A swollen belly that is tender to the touch, with a high fever, severe diarrhea or bloody stools, or being unable to eat or drink for more than 6 to 8 hours | Contact your provider | Today | MedlinePlus [8] |
| Gas with stomach or rectal pain, rectal bleeding, vomiting, fever or weight loss, or oily, foul-smelling stools | Contact your provider | Today | MedlinePlus [9] |
| Swelling that keeps getting worse and does not go away, or bloating with other unexplained symptoms | Your provider, at an appointment | At your next appointment | MedlinePlus [8] |
