Can Mounjaro Cause Gallstones? Risks Explained

Mounjaro (tirzepatide) can cause gallstones, and this risk is formally listed in the UK Summary of Product Characteristics. As a dual GIP and GLP-1 receptor agonist approved by the MHRA for type 2 diabetes and chronic weight management, Mounjaro affects gallbladder motility and can promote rapid weight loss, both of which are recognised contributors to gallstone formation. Understanding why this risk exists, who is most vulnerable, and what symptoms to watch for is essential for anyone taking or considering this medicine.

Can Mounjaro cause gallstones?

Yes, Mounjaro (tirzepatide) lists cholelithiasis and cholecystitis as known adverse effects in its UK SmPC. The risk is shared across the GLP-1 receptor agonist class and should be discussed with a prescriber.

Yes, Mounjaro (tirzepatide) can increase the risk of gallstones, and this is reflected in the UK Summary of Product Characteristics (SmPC). Mounjaro is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, authorised by the MHRA both for the management of type 2 diabetes and for chronic weight management in adults.^[1][4] Cholelithiasis (gallstones) and cholecystitis (inflammation of the gallbladder) are listed as known adverse effects in the SmPC (sections 4.4 and 4.8).

The association is not unique to tirzepatide. Gallstone formation is a recognised risk across the GLP-1 receptor agonist class, including semaglutide (Wegovy, Ozempic) and liraglutide (Saxenda).^[6][9] The risk appears to be linked partly to the pharmacological effects of these medicines on gallbladder function and partly to the rapid weight loss they can produce.

The SmPC does not quantify the absolute risk as low or high, and patients should be aware that gallbladder-related events have been reported. The benefits of treatment, including improved blood glucose control and meaningful weight reduction, are weighed against this and other risks by the prescribing clinician on an individual basis. It is important that patients and clinicians are aware of the risk so that symptoms can be recognised promptly.

If you are considering a weight-management consultation, Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, where Mounjaro is one option a prescriber may consider if it is clinically appropriate.

Anyone who develops symptoms suggestive of gallbladder disease during treatment should contact their GP promptly rather than waiting for a routine review.

Why do GLP-1 medicines increase the risk of gallstones?

GLP-1 receptor activation reduces gallbladder emptying, concentrating bile and promoting cholesterol crystal formation. Rapid weight loss further increases bile cholesterol secretion, compounding the pharmacological risk.

Tirzepatide is a dual GIP and GLP-1 receptor agonist. The increased risk of gallbladder events seen with this class of medicine is thought to involve two main mechanisms: effects on gallbladder motility and the metabolic consequences of rapid weight loss. Both are recognised in the clinical literature on GLP-1 receptor agonists, and the tirzepatide SmPC acknowledges gallbladder disease as a known adverse effect.

First, GLP-1 receptors are present in the gallbladder wall, and activation of these receptors has been associated with reduced gallbladder emptying in studies of GLP-1 receptor agonists.^[7][8] Bile that remains in the gallbladder for longer periods becomes more concentrated, and cholesterol crystals can begin to form, eventually developing into gallstones. This effect on gallbladder motility is considered a pharmacological consequence of the medicine's mechanism of action, though the precise contribution of the GIP component in tirzepatide is less well characterised.

Second, rapid weight loss, regardless of its cause, is a well-established independent risk factor for gallstone formation. When the body breaks down fat quickly, the liver secretes more cholesterol into bile, further increasing the likelihood of crystal formation.^[10][11] Because Mounjaro can produce substantial and relatively rapid reductions in body weight, this metabolic effect may compound the direct pharmacological risk. The magnitude of weight loss, rather than the specific medicine, is thought to be the key driver of this component of risk.

It is worth noting that obesity itself is also a significant risk factor for gallstones, so some individuals starting Mounjaro for weight management already carry an elevated baseline risk before treatment begins.^[12][13] The net clinical picture is therefore complex: the medicine may increase gallstone risk, but the underlying condition being treated also predisposes to gallbladder disease. Clinicians weigh these factors when assessing suitability for treatment and when advising on monitoring during therapy.

What symptoms of gallstones should I watch out for?

The key symptom is severe cramping pain in the upper right abdomen, often after a fatty meal, which may radiate to the right shoulder or back. Jaundice, fever, dark urine, or pale stools require prompt medical attention.

Gallstones do not always cause symptoms, but when they do, the most characteristic feature is biliary colic: a severe, cramping pain in the upper right abdomen or the centre of the abdomen, which may radiate to the right shoulder or back. The pain typically comes on suddenly, often after a fatty meal, and can last from a few minutes to several hours before easing.

Other symptoms that may indicate gallbladder disease include:

• Nausea and vomiting accompanying the abdominal pain

• Jaundice (yellowing of the skin or whites of the eyes), which may suggest a gallstone has moved into the bile duct

• Dark urine or pale stools, which can accompany jaundice

• Fever and chills, which may indicate infection (cholecystitis or cholangitis)

• Persistent upper abdominal discomfort or bloating after meals

Because tirzepatide is associated with a class risk of pancreatitis, it is also important to be aware of symptoms that may suggest acute pancreatitis: sudden, severe pain in the upper abdomen or centre of the abdomen that may radiate through to the back, often accompanied by nausea and vomiting. Gallstones are a recognised cause of pancreatitis. If you develop these symptoms, seek urgent medical attention.

If you experience severe abdominal pain, jaundice, or fever alongside abdominal pain, contact your GP promptly. If symptoms are severe and accompanied by signs of serious illness such as high fever, rigors, or rapidly worsening pain, call 999 or go to your nearest accident and emergency department, as these may indicate a complication such as acute cholecystitis, cholangitis, or pancreatitis requiring urgent assessment.

Milder or intermittent symptoms that do not suggest an emergency should be discussed with your GP, who can arrange appropriate investigations such as an abdominal ultrasound. Do not stop Mounjaro without first speaking to your prescriber, as abrupt discontinuation may affect your diabetes or weight management.

Who is most at risk of developing gallstones on Mounjaro?

Women, older adults, people with obesity, and those with a personal or family history of gallstones carry the highest baseline risk. Rapid weight loss during treatment further elevates that risk.

Certain individuals are at higher baseline risk of developing gallstones and may need closer monitoring when starting Mounjaro. Identifying these risk factors before treatment begins allows clinicians to have an informed discussion and put appropriate follow-up in place.

Key risk factors include:

• Female sex: Women, particularly those who have been pregnant or who use oestrogen-containing contraceptives, have a higher background risk of gallstones

• Older age: The risk of gallstone disease increases with age

• Obesity: A higher body mass index is independently associated with gallstone formation, and many people starting Mounjaro for weight management will already carry this risk

• Rapid weight loss: Those who lose weight quickly face a greater risk of gallstone formation during the weight-loss phase, regardless of the method used

• Personal or family history of gallstones: A previous episode of gallstone disease or a close family member with the condition increases individual risk

• Certain medical conditions: Conditions such as Crohn's disease and other ileal disorders, haemolytic anaemia, liver cirrhosis, and diabetes are associated with higher gallstone rates^[13][14]

• Prolonged fasting or very low-calorie diets: These reduce gallbladder emptying and increase bile concentration

People with several of these risk factors should discuss them with their prescriber before starting treatment. A baseline abdominal ultrasound is not a routine requirement for all patients starting Mounjaro; it is a clinical decision reserved for selected scenarios at the prescriber's discretion, based on individual risk assessment.

How is gallstone disease managed if it develops during treatment?

Management follows NICE CG188 and ranges from dietary modification and analgesia to laparoscopic cholecystectomy for symptomatic cases. Whether to continue Mounjaro is a clinical decision made by the prescribing clinician.

The management of gallstone disease that develops during Mounjaro treatment depends on whether the gallstones are causing symptoms and how severe those symptoms are. Asymptomatic gallstones discovered incidentally, for example on an ultrasound arranged for another reason, do not always require active treatment and may simply be monitored.

For symptomatic gallstones, the standard approach in the UK follows NICE guidance on gallstone disease (NICE CG188). Management options include:

• Dietary modification: Reducing fat intake can help limit the frequency and severity of biliary colic while awaiting further assessment

• Analgesia: Pain relief, typically with non-steroidal anti-inflammatory drugs (NSAIDs) or opioids in more severe cases, is used to manage acute episodes

• Laparoscopic cholecystectomy: Surgical removal of the gallbladder is the definitive treatment for symptomatic gallstones and is the most commonly performed procedure in the UK for this condition. NICE recommends early laparoscopic cholecystectomy for acute cholecystitis where the patient is fit for surgery^[16][17]

• Antibiotics: Where infection is suspected, such as in cholecystitis or cholangitis, antibiotic treatment is used alongside other management, guided by clinical judgement

• Endoscopic retrograde cholangiopancreatography (ERCP): This procedure may be needed if a gallstone has migrated into the common bile duct

The question of whether to continue or pause Mounjaro during gallstone management is a clinical decision that should be made by the prescribing clinician, taking into account the severity of gallbladder disease, the patient's overall health, and the benefits of ongoing treatment. Stopping Mounjaro abruptly without medical advice is not recommended. Your GP or specialist can advise on the most appropriate course of action based on your individual circumstances and can refer you to a surgical team if needed.

What should I tell my doctor before starting Mounjaro?

Disclose any history of gallstones, pancreatitis, diabetic retinopathy, kidney or liver problems, and all current medicines. Women should discuss contraception, as slowed gastric emptying may reduce oral contraceptive absorption.

Before starting Mounjaro, you should give your prescriber a full medical history so that they can assess your individual risk profile and ensure the medicine is appropriate for you. This is particularly important in relation to gallbladder disease, but also covers a range of other conditions relevant to the dual GIP and GLP-1 receptor agonist class.

Tell your prescriber if you have or have had:

• A personal or family history of gallstones or gallbladder disease

• Pancreatitis (inflammation of the pancreas): the UK Mounjaro SmPC (sections 4.4 and 4.8) states that acute pancreatitis has been reported with tirzepatide, including post-marketing reports of necrotising pancreatitis and reports with a fatal outcome

• Diabetic eye disease (retinopathy), particularly pre-existing pre-proliferative or proliferative diabetic retinopathy, as rapid improvement in blood glucose control may be associated with transient worsening in this subgroup

• Kidney or liver problems

• Any current medicines, including over-the-counter products and supplements: the UK SmPC (section 4.5) notes that Mounjaro slows gastric emptying, which may reduce the rate of absorption of oral medicines taken at the same time

Pregnancy, breastfeeding and contraception: The UK Mounjaro SmPC (section 4.6) advises that Mounjaro should not be used during pregnancy or breastfeeding, and that women of childbearing potential should use effective contraception during treatment. The SmPC specifically advises using an additional non-oral contraceptive method for four weeks after starting Mounjaro and for four weeks after each dose increase, because slowed gastric emptying may reduce the absorption of oral contraceptive pills.

If you experience any suspected side effects during treatment, these can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Scientific References

1. Mounjaro KwikPen 2.5mg solution for injection in pre-filled pen – Summary of Product Characteristics.
2. Tirzepatide for managing overweight and obesity (TA1026) – Practical guide.
3. Tirzepatide: a medicine to manage type 2 diabetes and weight.
4. Mounjaro (tirzepatide) – EPAR Product Information.
5. MHRA authorises diabetes drug Mounjaro (tirzepatide) for weight management and weight loss.
6. Association of Glucagon-Like Peptide-1 Receptor Agonist Use With Risk of Gallbladder and Biliary Diseases.
7. Physiology and Pharmacology of Effects of GLP-1-based Therapies.
8. New Avenues in the Regulation of Gallbladder Motility – Implications for the Use of Glucagon-Like Peptide-Derived Drugs.
9. Incretin-based therapy and acute cholecystitis: a review of case reports and EudraVigilance spontaneous adverse drug reaction reporting database.
10. The role of gallbladder emptying in gallstone formation during diet-induced rapid weight loss.
11. Gallbladder motility and gallstone formation in obese patients following very low calorie diets.
12. Gallstones, obesity, and jejunoileostomy.
13. Epidemiology of gallbladder disease: cholelithiasis and cancer.
14. Risk Factors for Gallstones in Crohn's Disease.
15. Incidence and risk factors for gallstones in patients with inflammatory bowel disease: a large case-control study.
16. Gallstone disease: diagnosis and management. Clinical guideline CG188.
17. Quality statement 1: Acute cholecystitis – Gallstone disease quality standard QS104.
18. GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists: strengthened warnings on acute pancreatitis including necrotising and fatal cases.
19. Mounjaro (tirzepatide) – EPAR Assessment Report Variation.
20. Early worsening of diabetic retinopathy in individuals with type 2 diabetes treated with tirzepatide.
21. Glucagon-Like Peptide-1 Receptor Agonists and the Eye: Ocular Safety, Retinal Outcomes, and Clinical Implications.
22. GLP-1 receptor agonists and serious adverse events: Evidence, uncertainty and clinical implications.

Frequently Asked Questions