Does Mounjaro Affect the Gallbladder?

How does Mounjaro interact with the gallbladder?

The gallbladder stores bile, which the digestive system uses to break down dietary fat. Normally it contracts after a meal, pushing bile into the small intestine. GLP-1 receptor activity, which tirzepatide engages alongside GIP receptors, appears to slow this emptying process. Bile that sits in the gallbladder for longer has more opportunity to become concentrated and to form crystals that eventually harden into stones.

There is a second mechanism at work too. Tirzepatide produces substantial weight loss, and losing weight quickly, from any cause, shifts the balance of substances in bile in a way that favours stone formation. Both effects can operate together, which is why gallbladder symptoms appear in the clinical data for this class of medicine.

In the SURMOUNT-1 trial, involving thousands of adults, cholelithiasis (gallstones) and cholecystitis (gallbladder inflammation) were observed more often in the tirzepatide groups than in those receiving placebo. The NHS tirzepatide page lists these as uncommon side effects. Understanding the broader side-effect picture is part of how our prescribers assess whether Mounjaro is the right option for you. You can read about the full Mounjaro side-effect profile separately.

Who is more likely to develop gallbladder problems on Mounjaro?

Pre-existing gallbladder disease raises the risk. If you have had gallstones before, or a previous bout of cholecystitis, that history matters and should be disclosed during your consultation. Women, people over 40, those who are pregnant or have recently been pregnant, and people with a family history of gallstones are already at higher background risk, so the additional contribution from treatment is worth discussing with a prescriber.

The pace of weight loss also plays a role. Losing more than around 1–1.5 kg per week over an extended period is associated with gallstone formation in the general literature, and some people on higher doses of tirzepatide do lose weight at this rate. This is not a reason to avoid treatment if it is otherwise suitable for you, but it underlines why gradual dose titration and dietary support matter alongside the medicine itself.

People with a history of pancreatitis need a careful prescriber conversation before starting Mounjaro, partly because the gallbladder and pancreas share ductal anatomy — a gallstone that migrates can trigger pancreatitis. The reasons tirzepatide can cause gallbladder issues are explored in more detail if you want the fuller picture.

When should you get medical help?

Most gallbladder symptoms build gradually, but some need same-day attention. Seek urgent medical assessment if you develop any of the following while taking Mounjaro:

Persistent pain in the upper-right abdomen or centre of the stomach, especially if it radiates to your right shoulder or between your shoulder blades and lasts more than a few hours. Pain that starts after eating a fatty meal and then subsides is typical of biliary colic; pain that does not settle, or is accompanied by fever and shivering, points to something more serious such as cholecystitis or a blocked bile duct.

Yellowing of the skin or whites of the eyes (jaundice), very dark urine, or pale, chalky stools suggest bile-duct obstruction and need prompt evaluation. These are not symptoms to wait out over a weekend. If you feel unwell enough to question whether to contact a doctor, contact one. You can also read about what to do when you feel unwell on Mounjaro for guidance on managing other episodes of illness during treatment.

The MHRA encourages patients to report suspected side effects, including gallbladder problems, through the Yellow Card scheme. Reporting contributes to the ongoing safety monitoring of all medicines, including newer ones like Mounjaro that carry a Black Triangle (▼) status indicating additional surveillance.

Does having your gallbladder removed change anything?

People who have had a cholecystectomy (gallbladder removal) can still use tirzepatide, and the absence of a gallbladder removes the risk of gallstones and cholecystitis. Bile flows directly from the liver into the small intestine after surgery. Some people without a gallbladder experience looser stools or diarrhoea, and starting a medicine that can itself cause diarrhoea during dose adjustment is worth flagging with your prescriber so they can monitor your response carefully.

If you are in this position, our prescribers are used to discussing it. It is one of the questions that comes up regularly, and getting the right information at the assessment stage avoids surprises once treatment begins. The considerations for people who have had their gallbladder removed and are considering Mounjaro are covered in their own page. For a broad overview of the treatment itself, the Mounjaro treatment page is a good starting point, and details on cost are available on the Mounjaro cost page. Our prescribers discuss gallbladder history, current symptoms and overall suitability as part of every free consultation.