Short answer: Constipation is one of the most common side effects listed on GLP-1 labels. In the Wegovy weight-loss trials 24% of people on 2.4 mg reported it versus 11% on placebo, and in the Zepbound trials 11% to 17% did versus 5% on placebo. A 2025 nutrition advisory from four obesity and nutrition societies lists fluids, fiber from food added gradually, and, if needed, options like magnesium or polyethylene glycol, which are worth checking with your prescriber or pharmacist first.
Each label reports constipation from its own placebo-controlled trials. The numbers are not directly comparable between products, because the trials enrolled different people for different lengths of time, but they show the size of the effect against placebo:
| Medicine and trials | Placebo | On the medicine |
|---|---|---|
| Wegovy 2.4 mg, adults, weight reduction (up to 68 weeks) | 11% | 24% |
| Wegovy 2.4 mg and 7.2 mg, adults with obesity | 8% | 19% (2.4 mg), 20% (7.2 mg) |
| Zepbound 5, 10 and 15 mg, adults, weight reduction (up to 72 weeks) | 5% | 17%, 14% and 11% |
| Ozempic 0.5 and 1 mg, type 2 diabetes | 1.5% | 5% and 3.1% |
| Mounjaro 5, 10 and 15 mg, type 2 diabetes | 1% | 6%, 6% and 7% |
The Mounjaro label adds that in a large cardiovascular trial in adults with type 2 diabetes, 13% of people on Mounjaro reported constipation. The weight-loss doses and trials show higher rates than the diabetes ones.
All four labels list ileus (the gut stopping moving), intestinal obstruction, and "severe constipation including fecal impaction" among reports collected after approval. These come from voluntary reports, so the labels say their frequency cannot be reliably estimated.
The labels also carry a warning on severe stomach and gut side effects. In the Zepbound weight-loss trials, severe gastrointestinal reactions were reported in 1.7% to 3.1% of people on the drug versus 1% on placebo; in the Wegovy trials, 4.1% versus 0.9%. Both labels say the drug is not recommended for people with severe gastroparesis.
The Patient Information leaflets say to tell your healthcare provider if you have stomach problems that are severe or will not go away.
In 2025 the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society published a joint advisory on nutrition during GLP-1 treatment. On constipation it says the problem is common with weight loss and "should be managed proactively". The steps it lists:
The advisory also notes that some anti-nausea medicines, such as ondansetron, can worsen constipation. Over-the-counter products can still interact with other medicines and health conditions, so a pharmacist or prescriber is the right check before starting one.
The labels connect gut side effects to the kidneys. Their patient leaflets say diarrhea, nausea and vomiting can cause a loss of fluids (dehydration) that may lead to kidney problems, and that "it is important for you to drink fluids to help reduce your chance of dehydration". The advisory adds that extended constipation can lead to reactive diarrhea, so the two problems can alternate.
Logging bowel changes next to dose days and dose increases makes the pattern clear: whether it started with a step-up, how long it lasts, and whether a change helped. Dose Track lets you log side effects against each dose.
Read more on Dose Track: Wegovy side effects · Zepbound side effects · Ozempic side effects · Mounjaro side effects · GLP-1 side effects week by week · GLP-1 nausea: what the labels say