How common
On Wegovy 2.4 mg, 30% reported diarrhea at least once, against 16% on placebo.[1] On Zepbound it was 19%, 21% and 23% at 5, 10 and 15 mg, against 8%.[2] On the lower diabetes doses the rates were lower: 8.5 to 8.8% on Ozempic against 1.9%.[3]
How long it lasts
In the pooled semaglutide trials, the median diarrhea episode lasted 3 days. Like nausea, most first episodes happened during the dose build-up, and prevalence peaked around week 20.[4] The Zepbound label also reports that most nausea, vomiting and diarrhea happened during dose escalation and decreased over time.[2]
Why the labels mention kidneys
Both labels carry a warning about acute kidney injury from volume depletion: losing fluid through vomiting or diarrhea, often while drinking less because appetite is down, can reduce blood flow to the kidneys. After the drugs were marketed, some reported cases needed hemodialysis.[1][2] In the Zepbound trials, acute kidney injury was reported in 0.5% versus 0.2% on placebo.[5] This is the practical reason to keep up fluids during a bad patch, and to tell the prescriber if it does not settle.
When to call
- Diarrhea or vomiting that lasts more than a day or two, or that you cannot keep up with
- Very little urine, dark urine, dizziness on standing, a racing heart (signs of dehydration)
- Blood in the stool or black stool, or severe belly pain
Heard vs evidence
The short version
Short on the way. A 35-second captioned version of this page is in production for the Fewer Bites channel. It will be embedded here when it is live.
Questions to bring to your prescriber
Print these or screenshot them. They are conversation starters, not a checklist of things to do.
- How much fluid should I aim for on a bad day, given my heart and kidney history?
- Are any of my medicines (water pills, blood pressure pills, NSAIDs, metformin) a problem if I get dehydrated?
- How many days of diarrhea before you want me to call?
Education, not advice. This page explains what trials, labels and guidelines report. It does not tell anyone to start, change or stop a medicine. Your prescriber knows your history; this page does not.
Sources
- Novo Nordisk / FDA. Wegovy (semaglutide) injection and tablets, prescribing information, revised 06/2026. label
- Eli Lilly / FDA. Zepbound (tirzepatide) prescribing information, revised 08/2026. label
- Novo Nordisk / FDA. Ozempic (semaglutide) prescribing information, revised 05/2026. label
- Wharton S et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg: post hoc analysis of STEP 1–3. Diabetes Obes Metab 2022;24:94–105. primary read · post hoc · industry-funded
- Fewer Bites nausea dossier: Zepbound pooled acute kidney injury rate 0.5% vs 0.2% (from the Zepbound prescribing information). label via dossier
- Rubino DM et al. Gastrointestinal tolerability of tirzepatide: post hoc analysis of SURMOUNT-1 to -4. Diabetes Obes Metab 2025;27:1826–35. primary read · post hoc · industry-funded