MHRA says users of jabs such as Wegovy and Mounjaro reported inflamed pancreas – which can cause agonising abdominal pain – before their deaths as a major investigation has been launched
A probe has been launched into why ten people died after reporting a severe side effect to weight loss injections.
The Medicines and Healthcare products Regulatory Agency (MHRA) has launched an investigation after hundreds of users reported problems with their pancreas. The regulator’s ‘Yellow Card’ scheme will now ask anyone who reports pancreatitis after taking the appetite-suppressing jabs to provide a DNA sample. It comes after Government ministers and some health leaders have called for the injections to be more widely available to tackle Britain’s obesity epidemic and targeted at areas of high unemployment to help get people back to work.
Professor Matt Brown, chief scientific officer of Genomics England, which will also run the study, said: “GLP-1 medicines like Ozempic and Wegovy have been making headlines, but like all medicines there can be a risk of serious side effects. We believe there is real potential to minimise these with many adverse reactions having a genetic cause.”
Weight loss jabs slow digestion and reduce appetite by mimicking hormones which regulate hunger and feelings of fullness. They are designed to act like one of these hormones, known as glucagon-like peptide 1 (GLP-1).
Last year it was reported that Susan McGowan was the first Brit believed to have died after taking weight loss injections. The 58-year-old took two Mounjaro injections before her death in September. Susan’s death certificate listed multiple organ failure, septic shock and pancreatitis as the immediate cause. It was believed to be the first confirmed death linked to a GLP-1 injection but it is not known whether her case was reported to the Yellow Card scheme.
Pancreatitis is inflammation of the organ located behind the stomach that aids in digestion and blood sugar regulation. It can cause sudden, severe abdominal pain, often radiating to the back. Other symptoms are nausea, vomiting, fever and a rapid heartbeat.
The Yellow Card scheme is the way anyone can report to the MHRA if they have had an adverse reaction to a drug. The MHRA data shows:
- 181 reported cases of acute and chronic pancreatitis linked to Mounjaro. Five of these people died
- 113 cases of acute and chronic pancreatitis linked to semaglutide – branded as Ozempic for diabetes and Wegovy for obesity – and one person died
- 116 users of the weight loss jab Saxenda reported having pancreatitis and one died
- Exenatide, known by its brand names Byetta and Bydureon, was linked to 101 similar reactions after which three died
These cases are not confirmed as being caused by the medicines but the person who reported them suspected they were.
It comes after data released from the MHRA under Freedom of Information laws found there had been a total of 111 “suspected adverse drug reactions with a fatal outcome” up to May 2025. Responding to a freedom of information request from Chemist + Druggist, the MHRA added: “Underlying or previously undiagnosed illness unrelated to the medicine can also be factors in such reports.”
However the latest data release focuses on fatal cases where side effects affected the pancreas.
Dr Alison Cave, MHRA’s chief safety officer, said: “Evidence shows that almost a third of side effects to medicines could be prevented with the introduction of genetic testing, it is predicted that adverse drug reactions could cost the NHS more than £2.2 billion a year in hospital stays alone. Information from the Yellow Card Biobank will help us to better predict those most at risk of adverse reactions – enabling patients across the UK to receive the safest medicine for them, based on their genetic makeup.”
When a Yellow Card report is received, the MHRA will contact patients to ask if they would be willing to take part in the study. Patients will be asked to submit more information and a saliva sample which will be assessed to explore whether some people are at a higher risk of acute pancreatitis when taking these medicines due to their genes.
GLP-1 agonists can lower blood sugar levels in people living with type 2 diabetes and can also be prescribed to support some people with weight loss. Recent estimates suggest that about 1.5 million people in the UK are taking weight loss jabs, mostly via private prescriptions. Some have reported having to stop taking them due to side effects, particularly nausea.
The new study is part of the UK Biobank project which is the biggest of its kind in the world and holds genetic data on half a million Brits.
Dr Cave added: “To help us help you, we’re asking anyone who has been hospitalised with acute pancreatitis while taking a GLP-1 medicine to report this to us via our Yellow Card scheme. Even if you don’t meet the criteria for this phase of the Biobank study, information about your reaction to a medication is always extremely valuable in helping to improve patient safety.”
It comes after GPs started offering the jab Mounjaro this week with it being prescribed first to those most overweight. Before it was only prescribed to on the NHS to patients already accessing specialist weight management clinics.
A spokesperson for Novo Nordisk, which manufactures Wegovy and Ozempic, 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 GLP1 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.
“We continuously collect safety data on our marketed GLP-1 medicines and work closely with the authorities to ensure patient safety. 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 spokesman for Eli Lilly, which makes 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. Adverse events should be reported under the MHRA’s Yellow Card scheme, but may be caused by other factors, including pre-existing conditions.
“The Mounjaro Patient Information Leaflet warns that inflamed pancreas – acute pancreatitis – is an uncommon side effect which may affect up to one in 100 people. It also advises patients to talk to their doctor or other healthcare professional before using Mounjaro if they have ever had pancreatitis.
“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.”
NHS leaders warn jabs are not ‘quick fix’
Prescribing guidelines state that weight loss injections should be part of a comprehensive weight management plan including tailored diet and exercise advice.
Side effects – particularly nausea and stomach cramps – can mean people stop taking the jabs. Some also find they can no longer afford the private prescriptions.
The injections can see users lose around a fifth of their body weight but, crucially, this includes muscle as well as fat.
Without drastic lifestyle changes research shows people pile fat back on a year after they stop taking the injections – but not the muscle. This makes it harder for them to lose weight again in future as they have less muscle to burn calories.
Anyone considering the injections should consult their GP.