In short
Overview
Most Mounjaro side effects are digestive, mild and strongest after a dose increase. Severe or persistent abdominal pain needs immediate medical assessment.
Direct Answer
The common side effects of Mounjaro (tirzepatide) are nausea, diarrhoea, vomiting, constipation and abdominal pain, mostly mild and during dose increases. Across GLP-1-based medicines, nausea affects 25 to 40 percent of people and vomiting, diarrhoea or constipation 10 to 20 percent.
Severe abdominal pain that spreads to the back, with or without vomiting, is a warning sign of pancreatitis and needs medical help immediately; do not wait for a clinic callback (MHRA, 2026).
Who This Applies To
- People who started Mounjaro and feel unwell.
- People with side effects after a dose increase.
- People unable to keep fluids down.
- People planning to start Mounjaro.
Option Comparison / Decision Criteria
Which Mounjaro side effects need which response?
Mounjaro side effects fall into 3 levels, set out in the table.
| Side effect | Response |
|---|---|
| Mild nausea, bloating, constipation | Smaller meals, fluids, review at the next visit |
| Vomiting or diarrhoea that stops you drinking | Contact the prescriber, risk of dehydration and kidney strain |
| Severe abdominal pain spreading to the back | Emergency care immediately |
| Pain under the right ribs with fever or yellow skin | Assessment for gallbladder disease the same day |
Why an In-Person Physician Review Matters
Why is a review better than pushing through?
A review is better because the next dose increase is delayed by 4 weeks when side effects are not tolerated, a standard step in clinical guidance. Dehydration from vomiting or diarrhoea strains the kidneys, so fluids and kidney function are checked when symptoms persist.
Frequently Asked Questions
Yes, nausea is the most common side effect and usually settles within days to weeks of each dose increase.
Severe, persistent abdominal pain, especially spreading to the back with or without vomiting, can be pancreatitis. Seek medical help immediately and do not wait for a routine appointment or callback.
Yes, constipation is a common side effect; constant pain, vomiting or no passing of wind needs prompt assessment.
A missed dose is taken within 4 days; after 4 days it is skipped and the next dose follows on the usual day.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
- Mounjaro KwikPen: Summary of Product Characteristics
- GLP-1 and dual GLP-1/GIP receptor agonists: strengthened warnings on acute pancreatitis
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.