EN
Home/United Kingdom/Blog/Can Mounjaro or Wegovy cause pancreatitis or gallstones?
UKUnited Kingdom Side effects and safety

Can Mounjaro or Wegovy cause pancreatitis or gallstones?

The MHRA's January 2026 warning, how often the UK labels say these problems happen, what large reviews show, and the warning signs.

GLP Guidebook teamPublished 12 Oct 20268 min read21 sourcesWritten from published sources

Written for the UK. Reading from India? India version

The short answer

They can, but pancreatitis is uncommon: the UK labels put it at up to 1 in 100 people. Gallstones are common, up to 1 in 10. In January 2026 the MHRA added warnings about rare necrotising and fatal pancreatitis. Severe stomach pain that won't go away needs urgent help.

Key takeaways

  • Pancreatitis is uncommon, up to 1 in 100 people, on the UK labels for Wegovy, Ozempic, Mounjaro and Saxenda, and gallstones are common, up to 1 in 10.1,2,3,4
  • In January 2026 the MHRA strengthened every UK GLP‑1 label to mention rare necrotising and fatal pancreatitis.5
  • The MHRA received 1,296 Yellow Card reports of pancreatitis linked to these medicines between 2007 and October 2025, 19 of them fatal.5
  • A 2022 review of 76 trials found about 27 extra gallbladder or bile-duct problems per 10,000 people on GLP‑1 medicines each year.6
  • The MHRA warning sign is severe, persistent stomach pain that may spread to the back and come with nausea or vomiting.5
On this page
  1. What are pancreatitis and gallbladder disease?
  2. What did the MHRA change in January 2026?
  3. How common are they on the UK labels?
  4. What do large reviews show?
  5. Why does losing weight quickly raise gallstone risk?
  6. What are the warning signs?
  7. How do you report it, and what is the Yellow Card Biobank?
  8. Questions people ask
  9. How we researched this

What are pancreatitis and gallbladder disease?

Acute pancreatitis is a sudden, painful swelling of the pancreas that needs urgent hospital treatment. Gallstones, small stones in the gallbladder, are one of its two commonest causes, with alcohol.7,8

Before you go further
  • GLP‑1 medicines are prescription-only in the UK. On the NHS or privately, a healthcare professional has to assess you before a prescription is issued.9
  • The label facts here come from the UK product information (the SmPC, the official label each maker publishes on the electronic Medicines Compendium). Where we use a US or EU label instead, we say so.
  • Every risk of these medicines is in Guide 5: Side effects and risks.
  • This post describes labels, guidance and trials. It is not a plan for your treatment, and no dose or brand guarantees any result.

The pancreas sits in the middle of your tummy. It helps you digest food and makes hormones such as insulin.7 Most people recover fully, but some develop serious problems, such as part of the pancreas dying (necrosis).7

The gallbladder is a small organ in the top of your tummy that helps you digest food. Most people with gallstones have no symptoms.8 A stone that blocks a bile duct can cause pain, an inflamed gallbladder (cholecystitis) or pancreatitis.8

The NHS says gallstones are more likely if you are over 40, a woman, living with obesity, have diabetes, or have lost weight quickly.8

What did the MHRA change in January 2026?

It strengthened the warning in every UK GLP‑1 label to mention rare necrotising and fatal pancreatitis. It says the overall risk is still uncommon.5

The update covers dulaglutide, exenatide, liraglutide, semaglutide and tirzepatide.5 Between 2007 and October 2025, the MHRA received 1,296 Yellow Card reports of pancreatitis linked to these medicines. Of those, 19 were fatal and 24 were necrotising.5

For scale, the MHRA estimates about 25.4 million packs were dispensed in the 5 years to late 2025. That count leaves out most online-only pharmacies.5 Yellow Card reports record suspected reactions.5

  • Private prescriptions. The MHRA warns doctors that private GLP‑1 prescriptions may not appear in medical records, so they should ask.5
  • If pancreatitis is confirmed, the medicine should not be restarted.5
  • Past pancreatitis. These medicines should be used with caution after a previous attack.5

The MHRA's chief safety officer called the risk of these severe effects "very small", but said patients should know the symptoms.10 About 1.6 million adults in Great Britain used GLP‑1s for weight between early 2024 and early 2025, UCL research estimates.10

How common are they on the UK labels?

Pancreatitis is uncommon on all four UK labels below, up to 1 in 100 people. Gallstones are common, up to 1 in 10.1,2,3,4

UK labelPancreatitisGallstonesInflamed gallbladder
Wegovysemaglutide, weightUncommon. Confirmed cases 0.2% vs under 0.1% on placebo1Common. 1.6% on 2.4 mg10.6% on 2.4 mg1
Ozempicsemaglutide, diabetesUncommon2Common2Not listed separately2
MounjarotirzepatideUncommon3Common in weight trials: 1.1% vs 1.0% on placebo30.6% vs 0.2% on placebo, weight trials3
Saxendaliraglutide, weightUncommon4Common4Uncommon4

UK label bands: common = 1 in 10 to 1 in 100 people; uncommon = 1 in 100 to 1 in 1,000. Percentages are the trial figures each UK label gives. Checked 12 Oct 2026 on the electronic Medicines Compendium.

Mounjaro's gallbladder figures depend on the trial. In its heart-failure trial, an inflamed gallbladder affected 2.2% on tirzepatide against 1.1% on placebo.3 In diabetes trials, gallstones were 0.3% against none.3 The Saxenda label says the extra gallstones were only partly explained by weight loss.4

What do large reviews show?

Reviews of many trials found a small rise in gallbladder problems. Two of three large reviews found no clear rise in pancreatitis; one found a slight rise.6,11,12,13

ReviewsGallbladder: extra cases on GLP-1 medicines
Extra cases compared with placebo or other treatments, from two separate reviews. They use different measures (per year, and over the whole trials), so the two rows can’t be compared with each other.
Gallbladder or bile-duct problems, 76 trials627 per 10,000each year
Gallstones, 55 trials112 per 1,000over the trials

Gallbladder. A 2022 review of 76 trials and 103,371 people found 37% more gallbladder or bile-duct problems in relative terms. That is about 27 extra cases per 10,000 people treated for a year.6 The rise was larger in weight-loss trials, at higher doses and with longer use.6

Pancreatitis. A 2025 review of 55 trials found these medicines "probably have little or no effect" on pancreatitis and other gut problems.11 A review of 21 heart trials, with 99,599 people, found no difference.13 A third review of 62 trials found a "slightly increased" risk, which faded when trials were split by other medicines taken.12

Why does losing weight quickly raise gallstone risk?

During weight loss, the liver puts more cholesterol into bile, and overloaded bile can form stones. The risk climbs as weight falls faster.14,15

This happens with any fast weight loss. In older studies, 10–12% of people developed new gallstones after 8–16 weeks of a low-calorie diet.14 A 1995 analysis found the risk rose steeply once weight fell faster than 1.5 kg (3.3 lb) a week.15

The UK Mounjaro label says its gallbladder events rose with the amount of weight lost.3 For Saxenda, weight loss explained only part of the extra risk.4

Free toolQuestions to take to your appointment

Build a short list, including past pancreatitis, gallstones and other medicines. No sign-up.

Make my list

What are the warning signs?

Severe stomach pain that won't go away, which may spread to your back, sometimes with vomiting. The MHRA says to get urgent medical help.5

Get help now: call 999 for a life-threatening emergency.16
  • Possible pancreatitis: sudden, severe tummy pain spreading to your back, a fast heartbeat or difficulty breathing.7
  • Possible gallstone problem: sudden severe tummy pain, pain spreading to the back with vomiting, a very high temperature, or yellow skin or whites of the eyes.8
The NHS says do not drive yourself to A&E.7 For urgent advice that is not an emergency, use NHS 111 in England, Scotland and Wales, online or by phone.17 Northern Ireland has no 111 service: call your GP practice or the GP out-of-hours service.18

Everyday stomach upset is very common on these medicines, more than 1 in 10 people on the UK Wegovy label.1 The MHRA notes that early pancreatitis can be mistaken for those common side effects or an infection.5 The difference is pain that is severe and doesn't settle.5

For tummy pain lasting more than 30 minutes, the NHS says to ask for an urgent GP appointment or use NHS 111.8 Our guide on side effects covers the everyday effects.

How do you report it, and what is the Yellow Card Biobank?

Report suspected side effects to the MHRA's Yellow Card scheme, online or in the app. Anyone can report, including patients.5,19

Since June 2025, the Yellow Card Biobank has been asking people hospitalised with acute pancreatitis on a GLP‑1 to report it. The MHRA may then invite them to give a saliva sample.20 It is studying whether genes make some people more likely to get pancreatitis on these medicines.20

More on reporting is in Mounjaro side effects, and reporting them.

RisksThe other risks, in brief
  • Stomach effects are very common (more than 1 in 10) on the UK Wegovy and Mounjaro labels.1,3
  • Dehydration from vomiting or diarrhoea can harm the kidneys.3
  • Hypos are more likely with insulin or a sulfonylurea.3
  • Breathing in stomach contents under general anaesthetic is a label warning: tell your anaesthetist.21
  • Not in pregnancy: stop semaglutide at least 2 months, and tirzepatide 1 month, before a planned pregnancy.9
Full detail in Guide 5: Side effects and risks →

Questions people ask

Can Mounjaro cause pancreatitis?

It can. The UK Mounjaro label rates acute pancreatitis as uncommon, up to 1 in 100 people, and the MHRA warns of rare severe and fatal cases.3,5

What does pancreatitis pain feel like?

The MHRA describes severe, persistent stomach pain that may spread to the back, with or without nausea and vomiting. The NHS says it may feel sharp and get worse after eating or lying down.5,7

Do weight-loss jabs cause gallstones?

Gallstones are common, up to 1 in 10 people, on the UK Wegovy, Ozempic, Mounjaro and Saxenda labels. Losing weight quickly raises the risk on its own.1,3,8

Can I restart Mounjaro after pancreatitis?

The MHRA says these medicines should not be restarted if pancreatitis is confirmed.5

How do I report a side effect?

Use the MHRA Yellow Card scheme, online or through the Yellow Card app. Patients can report directly.5,19

Shorter answers: How do I report a side effect (Yellow Card)? and When should I call 999 or 111 on a GLP-1?

How we researched this

On 12 Oct 2026 we read the pancreatitis and gallbladder sections of the UK labels for Wegovy, Ozempic, Mounjaro and Saxenda. We also read the MHRA’s January 2026 safety update and press release, its June 2025 Biobank release, and the NHS pages on pancreatitis and gallstones.

The review figures come from the papers’ abstracts, as checked for our India post. We did not divide the Yellow Card count by the pack count, because the two cover different years.

Before you move on

  • Pancreatitis is uncommon and gallstones common on the UK labels.
  • The MHRA added warnings of rare fatal pancreatitis in January 2026.
  • Severe stomach pain that won’t settle, especially into the back, needs urgent help.
  • Report suspected side effects on a Yellow Card.
Should I consider a GLP-1?I'm already on itDoctor questions tool

More from the UK blog

UKUnited KingdomMounjaro side effects, and reporting them UKUnited KingdomMounjaro and Wegovy before surgery UKUnited KingdomFake Mounjaro and illegal jabs
About GLP Guidebook

The monthly UK update

An independent guide to GLP‑1 medicines. We don't sell medicines, take drug-company money or earn clinic commissions. Once a month: NHS access changes, approvals, safety notices and recalls. How we write

Was this post easy to understand?

Sources

  1. Novo Nordisk. Wegovy FlexTouch (semaglutide) pens: UK summary of product characteristics (SmPC), date of revision 09/2026. Sections 4.1, 4.2, 4.4, 4.5, 4.6, 4.8, 5.1, 5.2, 6.3, 6.4. emc
  2. Novo Nordisk. Ozempic (semaglutide) pens: UK SmPC, date of revision 07/2026. Sections 4.1, 4.2, 4.4, 4.6, 4.8, 5.1, 5.2. emc
  3. Eli Lilly. Mounjaro KwikPen (tirzepatide): UK summary of product characteristics (SmPC, the UK label), date of revision 29 August 2026. Sections 4.2, 4.4, 4.5, 4.6, 4.8, 5.2, 6.4. emc
  4. Novo Nordisk. Saxenda (liraglutide) 6 mg/ml pen: UK SmPC, date of revision 11/2025. Sections 4.1, 4.2, 4.4, 4.6, 4.8, 5.1, 5.2, 6.3, 6.4. emc
  5. MHRA. Drug Safety Update: GLP‑1 receptor agonists and dual GLP‑1/GIP receptor agonists: strengthened warnings on acute pancreatitis, including necrotising and fatal cases. Volume 19, issue 6, 29 January 2026. gov.uk
  6. He L et al. Association of GLP‑1 receptor agonist use with risk of gallbladder and biliary diseases: a systematic review and meta-analysis of randomized clinical trials. JAMA Intern Med 2022;182:513–19. Declared interests: none reported. DOI · PMC8961394
  7. NHS. Acute pancreatitis. Opened 12 October 2026. nhs.uk
  8. NHS. Gallstones. Opened 12 October 2026. nhs.uk
  9. MHRA (Medicines and Healthcare products Regulatory Agency). GLP‑1 medicines for weight loss and diabetes: what you need to know. First published 5 June 2025, updated 5 February 2026. gov.uk
  10. MHRA. MHRA updates guidance for GLP‑1 prescribers and patients. Press release, 29 January 2026. gov.uk
  11. Chiang CH et al. Glucagon-like peptide-1 receptor agonists and gastrointestinal adverse events: a systematic review and meta-analysis. Gastroenterology 2025;169:1268–81. DOI · PMID 40499738
  12. Wen J et al. Evaluating the rates of pancreatitis and pancreatic cancer among GLP‑1 receptor agonists: a systematic review and meta-analysis of randomised controlled trials. Endocrinol Diabetes Metab 2025;8:e70113. Declared interests: none. DOI · PMC12457091
  13. Galli M et al. Cardiovascular effects and tolerability of GLP‑1 receptor agonists: a systematic review and meta-analysis of 99,599 patients. J Am Coll Cardiol 2025;86:1805–19. Some authors report fees from Novo Nordisk and Eli Lilly. DOI · PMID 40892610
  14. Erlinger S. Gallstones in obesity and weight loss. Eur J Gastroenterol Hepatol 2000;12:1347–52. DOI · PMID 11192327
  15. Weinsier RL, Wilson LJ, Lee J. Medically safe rate of weight loss for the treatment of obesity: a guideline based on risk of gallstone formation. Am J Med 1995;98:115–17. DOI · PMID 7847427
  16. NHS. When to call 999. Page last reviewed 3 February 2023. nhs.uk
  17. NHS. When to use NHS 111 online or call 111. Opened 12 October 2026. nhs.uk
  18. nidirect (Northern Ireland government). GP out of hours service. Opened 12 October 2026. nidirect.gov.uk
  19. MHRA. Yellow Card: making medicines and medical devices safer (reporting site; guest reports and the Yellow Card app). Opened 12 October 2026. yellowcard.mhra.gov.uk
  20. MHRA. If you take a GLP‑1 medicine and have been hospitalised by acute pancreatitis, the Yellow Card Biobank wants to hear from you. Press release, 26 June 2025. gov.uk
  21. MHRA. Drug Safety Update: GLP‑1 and dual GIP/GLP‑1 receptor agonists: potential risk of pulmonary aspiration during general anaesthesia or deep sedation. Volume 18, issue 6, 28 January 2025. gov.uk

Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error

How this post was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor, nurse or pharmacist before starting, stopping or changing any medicine. How we write