Hundreds of people have reported problems with their pancreas after taking weight loss drugs, with a new study launched to find out if there may be genetic risk factors.
Ten people have died after reportedly taking GLP-1 (glucagon-like peptide-1) receptor agonists, which are also used to treat diabetes.
None of the deaths are confirmed as being caused by the jabs, but those who reported the side effects suspect they may be.
The news comes as GPs get the green light to prescribe weight loss jabs for the first time, to patients with a BMI of 40 or above who also have related health conditions such as heart disease and high blood pressure.
The mass rollout will see around 220,000 people with the ‘greatest need’ receive Mounjaro, also known as tirzepatide, through the NHS over the next three years.
Until now, people could only access the drug through a special weight loss service, or for diabetes.
Data from the medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), shows that since the drugs were first licensed there have been hundreds of cases of acute and chronic pancreatitis among people taking GLP-1 medicines.
Side effects
Suspected cases of bad reactions to the jabs include:
- 181 reported cases of acute and chronic pancreatitis linked to tirzepatide – the active ingredient for Mounjaro. Five people died.
- 116 reported reactions of this kind linked to liraglutide, one of which was fatal.
- 113 cases of acute and chronic pancreatitis linked to semaglutide – the active ingredient for Ozempic and Wegovy. One person died.
- 101 reported reactions of this kind linked to exenatide, three people died.
- 52 reported reactions of this sort linked to dulaglutide and 11 reported reactions lixisenatide. No fatalities were linked to either drug.
It collects information on adverse effects of medicines under theYellow Card system, where patients are invited to submit their experience.
The MHRA wants to find out whether some patients could be more at risk of pancreas problems due to their genes.
Working alongside Genomics England for the Yellow Card Biobank project, it is now calling on people who have been admitted to hospital due to acute pancreatitis after taking the jabs to submit a side effects report to Yellow Card.
When it is received, patients will be contacted to ask if they would be willing to take part in the study, which would involve submitting more information and a saliva sample, so their DNA can be examined to see if there any possible risk factors can be identified.
How do the jabs work?
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.
By mimicking hormones that send a message to our brains that we are full up, they encourage patients to eat less.
Recent estimates suggest that about 1.5 million people in the UK are taking weight loss jabs sucyh as Wegovy and Mounjaro.

They have been hailed a ‘game-changer’ by health secretary Wes Streeting, who says they can save the NHS billions by solving the obesity crisis and even tackle employment by making people fit enough to work.
But health officials have stressed they are not a silver bullet and do come with side effects.
Most linked to the jabs are gastrointestinal including nausea, constipation and diarrhoea.
The medical regulator recently warned that Mounjaro may make the oral contraceptive pill less effective in some patients.
Patients typically regain most of their lost weight unless they keep taking the jabs long-term, studies have shown.
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.’
‘It’s not all sunshine and rainbows’

Ashley O’Driscoll, from Dublin, told Metro how she lost half her weight on Ozempic, but piled it back on when she could no longer afford the prescription.
Having endured years of failed diets, slimming clubs and exercise regimes, Ashley admits the jab felt like a last resort when the waiting list for surgery was too long – and she wasn’t entirely convinced it would work.
She obtained a prescription from her doctor, picked up her first dose from the pharmacy, took it home and injected it into her abdomen. Despite a few mild side effects of headaches and nausea, Ashley’s weight started to fall away within the first week.
‘It was great; it started coming off very quickly and I noticed the “food noise” disappear,’ she remembers.
‘You’re not constantly thinking about your next meal and what you’re going to eat. It decreases your appetite and makes you feel full for longer.
‘On Ozempic, I might have a breakfast of porridge and honey and then not eat again for another six hours. I would have a soup or something really small for lunch, then a small dinner.’
But after losing 12 stone, she was left with sagging skin, and also fell ill with gallstones, which can happen with rapid weight loss.
‘Going on Ozempic was one of the best things I ever did, but it’s not all sunshine and rainbows,’ she said. ‘It brings with it a lot of trauma from being overweight and trying to accept your new body. I’m not there yet.
‘A lot of people think, “Oh, it’s just a case of you lose the weight and it’s over” – and it’s far from it. It’s trying to deal with and accept everything that comes with it, and it’s a work in progress. You have to maintain that weight. You’re always working on your body. It’s never ending.’
Professor Matt Brown, chief scientific officer of Genomics England, 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.
‘This next step in our partnership with the MHRA will generate data and evidence for safer and more effective treatment through more personalised approaches to prescription, supporting a shift towards an increasingly prevention-focused healthcare system.’
Manufacturers responded
A spokesperson for 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 (tirzepatide) Patient Information Leaflet warns that inflamed pancreas (acute pancreatitis) is an uncommon side effect (which may affect up to 1 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. ‘
A spokesperson for Novo Nordisk UK, which manufactures 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 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.’
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