Independent UK medicine guidance
Mounjaro and gallbladder inflammation (cholecystitis)
Cholecystitis is inflammation or infection of the gallbladder. It is a different and more serious problem than having gallstones, and it is a medical emergency rather than something to manage at home. In weight management it is listed as uncommon. This guide covers how it differs from ordinary gallstone pain and what to do.
Key facts
- Cholecystitis (gallbladder inflammation) is an uncommon side effect of Mounjaro in weight management: up to 1 in 100 people (UK leaflet, revised August 2026).
- In the type 2 diabetes cardiovascular disease study it was common, up to 1 in 10. It is not separately listed for adults treated for type 2 diabetes generally.
- It is a different problem from gallstones, which are common in weight management. Gallstones can cause cholecystitis but most people with gallstones do not develop it.
- Severe pain under the right ribs with fever, vomiting or yellowing of the skin or eyes is a medical emergency: call 999 or go to A&E.
How is it different from gallstones?
Gallstones are stones that form in the gallbladder. Many people have them without ever knowing. When a stone temporarily blocks a duct it causes an attack of pain that eventually settles.
Cholecystitis is what happens when the gallbladder itself becomes inflamed or infected, usually because a stone stays stuck. The pain does not settle in the same way, and the body starts showing signs of infection. It normally requires hospital assessment, antibiotics and sometimes surgery.
How common is it?
Cholecystitis and gallstones sit in different frequency bands, and they move in opposite directions between patient groups. Gallstones are common in weight management but uncommon in adults treated for type 2 diabetes alone. Cholecystitis is the reverse: uncommon in weight management, and common in the cardiovascular disease study. If you are taking Mounjaro for weight loss, gallbladder inflammation is the less likely of the two, but it is the more serious.
Symptoms to watch for
- Severe pain under the ribs on the right that does not settle
- Pain spreading to the right shoulder or shoulder blade
- A high temperature, shivering or sweating
- Feeling sick or being repeatedly sick
- Yellowing of the skin or the whites of the eyes
- Pain that is worse when you breathe in deeply or press the area
- Feeling generally very unwell, confused or weak
Rapid weight loss is itself a recognised risk factor for gallbladder problems, which is the most likely reason gallstones are reported more often in weight-management studies. Tell your prescriber if you have ever had gallstones, gallbladder inflammation or pancreatitis before starting or continuing treatment.
What to do
Contact NHS 111 urgently if abdominal pain lasts longer than 30 minutes.
Call 999 or attend A&E for severe pain under the right ribs, particularly with fever or shivering, repeated vomiting, jaundice, confusion, collapse or severe weakness.
Do not try to manage suspected gallbladder inflammation at home, and do not assume severe abdominal pain is an ordinary treatment side effect. Severe pain that spreads through to the back can also indicate pancreatitis, which needs the same urgent assessment.
Read the full guide to pancreatitis warning signsCommon questions
What is cholecystitis?
Cholecystitis is inflammation or infection of the gallbladder, usually caused by a gallstone becoming stuck. Unlike an ordinary gallstone attack, the pain does not settle and is joined by signs of infection such as fever or shivering. It normally needs hospital assessment, antibiotics and sometimes surgery.
How common is gallbladder inflammation on Mounjaro?
It is listed as uncommon in weight management, meaning it may affect up to 1 in 100 people. In the type 2 diabetes cardiovascular disease study reported in the leaflet revised in August 2026, it was common. Gallstones, which are a different problem, are common in weight management.
How do I tell gallbladder inflammation from a gallstone attack?
A gallstone attack tends to ease after a period of pain. Cholecystitis pain persists and is accompanied by a high temperature, shivering, repeated vomiting, jaundice or feeling generally very unwell. Persistent pain with a fever is the combination that needs emergency care rather than waiting.
Can I reduce the risk?
There is no guaranteed prevention. Rapid weight loss is a known risk factor for gallbladder problems, so avoiding crash dieting and aiming for a sustainable rate of weight loss is sensible, alongside a balanced diet and good hydration. Do not deliberately eat large amounts of fat to empty the gallbladder, as this can trigger pain if you already have stones.
Related guides
Sources: Mounjaro KwikPen UK Patient Information Leaflet (eMC) • Mounjaro Summary of Product Characteristics (eMC) • NHS gallstones guidance
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