# Diarrhoea on a GLP-1

> Mounjaro’s, Wegovy’s and Ozempic’s leaflets list diarrhoea as very common, more than 1 in 10 people, and both NHS pages list it. In two Zepbound trials, 19% to 23% reported it, against 8% on placebo. Wegovy’s and Ozempic’s leaflets say it can cause dehydration, and that drinking fluids is important to prevent it.

Canonical: https://jabwise.app/guides/diarrhoea. Sources checked 12 October 2026. General information, not medical advice: follow your prescriber.

## How common it is

Each leaflet’s own words for how common diarrhoea is, quoted as written. Zepbound’s label counts it among its most common side effects.

- **Mounjaro**: How common: "Very common (may affect more than 1 in 10 people)" ([Mounjaro KwikPen patient leaflet](https://www.medicines.org.uk/emc/product/15481/pil))
- **Zepbound**: How common: "The most common adverse reactions, reported in ≥5% of patients treated with ZEPBOUND are: nausea, diarrhea" ([Zepbound prescribing information](https://uspl.lilly.com/zepbound/zepbound.html))
- **Wegovy**: How common: "Very common: may affect more than 1 in 10 people" ([Wegovy FlexTouch patient leaflet](https://www.medicines.org.uk/emc/product/13800/pil))
- **Ozempic**: How common: "Very common (may affect more than 1 in 10 people)" ([Ozempic patient leaflet](https://www.medicines.org.uk/emc/product/9748/pil))

## What else they say

- **It usually eases**: Wegovy’s and Ozempic’s leaflets say diarrhoea usually goes away over time; Mounjaro’s says it decreases in most patients.
- **By dose in the trials**: In Zepbound’s trials, diarrhoea was reported by 19% on 5mg, 21% on 10mg and 23% on 15mg, against 8% on placebo.
- **Losing fluids**: Mounjaro’s leaflet says losing fluids at the start may reduce kidney function, and to avoid dehydration with plenty of fluids.
- **If it bothers you**: If a side effect bothers you or doesn’t go away, the NHS says a pharmacist or doctor may give advice on how to reduce it.

## Questions

### Is diarrhoea a side effect of Mounjaro?

Yes. Mounjaro’s leaflet lists it as very common, more than 1 in 10 people, and says it’s usually not severe and decreases over time in most patients.

### How long does it last?

None of the sources gives a timescale. Wegovy’s and Ozempic’s leaflets say it usually goes away over time; Zepbound’s label says most cases in its trials came while the dose was going up.

### When should I get help?

The NHS says call 111 if you think you’re having a serious side effect. Zepbound’s label asks you to tell your healthcare provider right away if diarrhoea doesn’t go away.

## In Jabwise: Side effects

Count the days it’s there. Each check-in asks “Any side effects currently?”, and Diarrhoea is one tap. Side Effects counts the days you felt it, over 7, 30 or 90 days, ready for your next review.

## Getting real advice

- **A pharmacist, your doctor or NHS 111**: If you’re not sure how to use your medicine, or a side effect bothers you or won’t go away. NHS 111 if you think you might be having serious side effects, or you’ve used too much. [NHS: Semaglutide](https://www.nhs.uk/medicines/semaglutide/), [NHS: Tirzepatide](https://www.nhs.uk/medicines/tirzepatide/), [NHS 111 online](https://111.nhs.uk/)
- **Report a side effect**: Anyone can, not only doctors. [Yellow Card (UK)](https://yellowcard.mhra.gov.uk/), [MedWatch (US)](https://www.fda.gov/safety/medwatch-fda-safety-information-and-adverse-event-reporting-program)

## Sources

- [Mounjaro KwikPen patient leaflet](https://www.medicines.org.uk/emc/product/15481/pil)
- [Zepbound prescribing information](https://uspl.lilly.com/zepbound/zepbound.html)
- [Wegovy FlexTouch patient leaflet](https://www.medicines.org.uk/emc/product/13800/pil)
- [Ozempic patient leaflet](https://www.medicines.org.uk/emc/product/9748/pil)
- [NHS: Tirzepatide](https://www.nhs.uk/medicines/tirzepatide/)
- [NHS: Semaglutide](https://www.nhs.uk/medicines/semaglutide/)