Short answer: Yes, it is one of the most common side effects. In the label trials, diarrhea was reported by 30% of adults on Wegovy 2.4 mg versus 16% on placebo, 19% to 23% on Zepbound versus 8%, 12% to 17% on Mounjaro versus 9%, and about 9% on Ozempic versus 2%. The labels say most of it happened while the dose was being raised. They also warn that diarrhea, nausea and vomiting can cause dehydration, which can lead to kidney problems.
Each US label has a table of side effects from its placebo-controlled trials. The diarrhea rows:
| Medicine and trials | On the medicine | Placebo |
|---|---|---|
| Ozempic, type 2 diabetes (0.5 mg and 1 mg) | 8.5% and 8.8% | 1.9% |
| Wegovy 2.4 mg, adults, weight reduction | 30% | 16% |
| Wegovy 2.4 mg, ages 12 and up | 22% | 19% |
| Mounjaro, type 2 diabetes (5, 10 and 15 mg) | 12%, 13% and 17% | 9% |
| Zepbound, weight reduction (5, 10 and 15 mg) | 19%, 21% and 23% | 8% |
The Zepbound row counts both diarrhea and "frequent bowel movements". The trials differ in who took part, the doses and how long they ran, and each label says rates from one drug's trials cannot be directly compared with another's. The weight-loss trials, with higher doses, reported more diarrhea than the diabetes trials.
Few people stopped because of it. In the Wegovy adult trials, 0.7% stopped treatment because of diarrhea, against 0.1% on placebo.
The labels tie stomach side effects to the start of treatment and each dose increase. The Ozempic label says most reports of nausea, vomiting and diarrhea "occurred during dose escalation". The Mounjaro and Zepbound labels say the same and add that these events "decreased over time".
That is one reason all four medicines start at a low dose and step up over weeks, as their dosing sections lay out. The week-by-week side effects guide walks through what the labels say for each stage.
Constipation is listed too, and some people have both at different times. The constipation answer covers that side.
All four labels have a warning about acute kidney injury from fluid loss. The patient leaflets say diarrhea, nausea and vomiting "may cause a loss of fluids (dehydration) which may cause kidney problems". They say it is important to drink fluids to lower that chance, and to tell your healthcare provider right away if nausea, vomiting or diarrhea does not go away.
The prescriber sections say kidney function should be monitored in people reporting side effects that could lead to fluid loss, especially when starting and when raising the dose. The kidney problems answer has the trial numbers.
Diarrhea can also matter for other medicines. The Mounjaro and Zepbound labels note that oral birth control pills may work less well after starting and after each dose increase; that is covered in the tirzepatide and birth control article.
The labels do not give diet steps for diarrhea; they list it as a side effect to report if it bothers you or does not go away. Notes that help a prescriber judge whether it is the medicine, the dose step, or something else:
Dose Track lets you log side effects next to each dose, so a pattern such as "two days after every shot" or "only in the week after going up" is easy to see and show.
Read more on Dose Track: Nausea on GLP-1s: what the labels say · GLP-1 side effects week by week · Ozempic side effects · Wegovy side effects · Mounjaro side effects · Zepbound side effects