Health guidance on weight loss drugs in the UK has been updated over a risk of a side effect with organ-destroying consequences.
The Medicines and Healthcare products Regulatory Agency (MHRA) has updated the product information for healthcare professionals and their patients over GLP-1 drugs like Ozempic, Wegovy and Mounjaro.
These drugs have been prescribed for Type-2 diabetes, while Wegovy and Mounjaro are available on the NHS for weight loss.
They've said there's a 'small risk of severe acute pancreatitis' for people taking these drugs, with it being a very rare side effect where a person's pancreas becomes swollen.
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Most people with this get better by themselves, but in more serious cases, there can be complications which result in stomach pain, nausea and vomiting.
In the most serious of cases it can even be fatal by causing multiple organ failure, with the NHS warning that one in five cases falls into the severe category which leads to complications the worst of which being death.
In this more serious case it can leave a person stuck in hospital for weeks or even months at a time for their recovery.
Between 2007 and October 2025, the MHRA received 1,296 YellowCard reports of pancreatitis associated with GLP-1 receptor agonists.
Meanwhile, it's estimated that around 1.6 million adults in England, Wales and Scotland used GLP-1 drugs to lose weight between 2024 and 2025, with a further 3.3 million interested in doing so throughout 2026.
Dr Alison Cave, chief safety officer at the MHRA, 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."
A spokesperson for Novo Nordisk, the manufacturer of Ozempic and Wegovy, said: "Patient safety is of the utmost importance to Novo Nordisk. Like all medications, side effects can occur and vary from patient to patient. The known risks and benefits of GLP-1 medicines are described in the Summary of Product Characteristics.
"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.
"Although the frequency of acute pancreatitis is uncommon, healthcare professionals should be aware that pancreatitis has been associated with GLP-1 and GLP-1/GIP receptor agonists, and to stay alert to signs and symptoms in their patients.
"We continuously collect safety data on our marketed GLP-1 medicines and work closely with the authorities to ensure patient safety. The MHRA tracks reports of all adverse events registered against medicines, and in rare instances pancreatitis has been associated with GLP-1 and GLP-1/GIP receptor agonists in its database stemming back to 2007, almost 20 years.
"The benefit-risk profile of our GLP-1 medicines remains positive, and we welcome any new research that will improve our understanding of treatments for people living with chronic diseases."
A statement from 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."
Joe Harker