Patients on weight-loss jabs and diabetes injections should be aware there is a small risk of developing severe acute pancreatitis, the UK medicines regulator has said.
About 1.6 million adults in England, Wales and Scotland used GLP-1 medication, such as semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro), between early 2024 and early 2025 to lose weight, according to recent research.
Patient information leaflets for Wegovy, Ozempic and Mounjaro list pancreatitis as an “uncommon” reaction, affecting about one in 100 patients.
Acute pancreatitis occurs when the pancreas, a gland located behind the stomach that aids in digestion, becomes suddenly inflamed. Symptoms include severe pain in the abdomen, nausea and fever, with patients often ending up in hospital.
While acknowledging that pancreatitis is rare, on Thursday the Medicines and Healthcare products Regulatory Agency (MHRA) updated its guidance, after an increase in reports of acute pancreatitis to the agency’s yellow card scheme, which monitors any adverse reactions to medications and medical devices in the UK.
To date, there have been 1,143 reports of acute and chronic pancreatitis to the yellow card scheme among patients taking semaglutide or tirzepatide, with 17 reported fatalities. Nearly all (973) were logged in 2025, of which 807 concerned tirzepatide and 166 were related to semaglutide. To date, there have been 146 reports of acute and chronic pancreatitis from those taking liraglutide and 61 from those taking dulaglutide.
Dr Alison Cave, the MHRA’s chief safety officer, said: “Patient safety is the MHRA’s top priority and we continually monitor the safety and efficacy of all licensed medicines. For the vast majority of patients who are prescribed GLP-1s, they are safe and effective medicines, which deliver significant health benefits.
“The risk of developing these severe side effects is very small, but it is important that patients and healthcare professionals are aware and alert to the associated symptoms.
“If you, or someone you care for, is taking GLP-1s and you notice symptoms such as severe, persistent stomach pain that may radiate to the back and may be accompanied by nausea and vomiting, then we advise you speak to a healthcare professional and report it via our yellow card scheme.”
Separately, the MHRA said that patients taking GLP-1s had been recruited to the Yellow Card Biobank study, a collaboration between the MHRA and Genomics England, which will investigate whether the risk of an inflamed pancreas can be influenced by an individual’s genes. The agency said: “It is hoped this will help to predict which patients may be most at risk of adverse reactions and prescribe the safest medicines accordingly.”
Responding to the announcement, a spokesperson for Novo Nordisk, which makes Wegovy and Ozempic, said: “Patient safety is of the utmost importance to Novo Nordisk. We recommend that patients take these medications only for their approved indications and under the strict supervision of a healthcare professional, who can also advise on potential side effects.
“We continuously collect safety data on our marketed GLP-1 medicines and work closely with the authorities to ensure patient safety.”
Eli Lilly, the manufacturer of Mounjaro, said: “Patient safety is Lilly’s top priority. We take reports regarding patient safety seriously and actively monitor, evaluate, and report safety information for all our medicines.
“The Mounjaro (tirzepatide) patient information leaflet warns that inflamed pancreas (acute pancreatitis) is an uncommon side-effect (which may affect up to 1 in 100 people) and advises patients to talk to their doctor or other healthcare professional before using Mounjaro if they have ever had pancreatitis. We continue to work with the MHRA to ensure that appropriate safety information is available to prescribers.
“We encourage patients to consult their doctor or other healthcare professional regarding any side-effects they may be experiencing and to ensure that they are getting genuine Lilly medicine.”