Published: 27 November 2025
Study Launched by MHRA and Genomics England
The UK Medicines and Healthcare products Regulatory Agency (MHRA), together with Genomics England, has launched a large-scale investigation into potential genetic links behind cases of pancreatitis reported in users of popular weight-loss injections, including Ozempic, Wegovy, and Mounjaro.
The study was prompted after hundreds of reports suggesting possible pancreas-related complications among people using GLP-1 receptor agonists, a class of drugs widely prescribed for weight management and type 2 diabetes.
While the reported cases have not been proven to be caused by the medications, regulators say the volume of alerts warrants a detailed genomic investigation.
Pancreas-Related Concerns: Hundreds of Reports
The MHRA has received around 400 reports describing acute and chronic pancreatitis, including a small number of fatal cases.
Officials stress, however, that the reports only indicate suspected reactions—not confirmed causation.
Some cases involved severe abdominal pain, persistent vomiting, and hospitalisation, leading researchers to investigate whether certain individuals may carry genetic variants that increase vulnerability.
Purpose of the New Study
The joint project aims to identify genetic risk factors that could predict which patients are most likely to experience serious side effects from GLP-1 therapies.
The ultimate goals are to:
- Reduce future adverse drug reactions,
- Help clinicians personalise treatment,
- And ensure safer prescribing as weight-loss injections become more widely used.
Researchers believe that pinpointing genetic sensitivities could be a major breakthrough in precision medicine.
MHRA Yellow Card Scheme Central to Data Collection
The investigation builds on patient submissions to the MHRA Yellow Card Scheme, the UK’s central reporting platform for suspected drug and medical device reactions.
Adults aged 18 and over who have been hospitalized after using GLP-1 drugs are being asked to file detailed reports.Participants will also submit saliva samples and additional medical information to support the genomic analysis conducted by Genomics England.
The collaboration marks one of the first efforts to integrate real-world side-effect reports with large-scale genetic sequencing.
Drug Details and Known Side-Effect Risks
GLP-1 drugs such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) list pancreatitis as an “uncommon” side effect.
Commonly recognised symptoms include:
- Upper abdominal pain
- Nausea and vomiting
- Fever
- Back pain
Other, more routine side effects reported by patients include nausea, constipation, diarrhoea, and reduced appetite—typical results of slowed digestion caused by GLP-1 medications.
Regulators emphasise that millions of people use these drugs safely each year, but the goal is to refine understanding of rare complications.
Statistical Highlights
Recent MHRA data show:
- 181 cases linked to Mounjaro (the largest share)
- 22 semaglutide-related cases recorded in 2025 alone
- More than one quarter of all pancreatitis reports occurred in 2025, reflecting soaring usage of weight-loss therapies
Officials note that increased prescribing, media attention, and better awareness likely contributed to the rise in reported cases.
Usage Concerns: Online Sales and Unregulated Access
Health authorities say one of the greatest challenges is estimating the true number of UK users of weight-loss injections.
A significant volume of Ozempic, Wegovy, and Mounjaro pens are believed to be purchased online, outside regulated medical channels.
This makes it harder to track side effects, ensure correct dosing, or verify the authenticity of products—raising additional safety concerns.Demand for GLP-1 drugs has surged as they become embedded in both formal weight-management programs and informal consumer-driven dieting trends.
Statements From MHRA and Genomics England
Officials from both organisations say the study could dramatically reshape how future medications are prescribed.Genomics England says early modelling suggests genetic testing could prevent up to one-third of severe adverse reactions.
The MHRA notes that adverse drug reactions cost the NHS an estimated £2.2 billion per year, reinforcing the importance of early detection.
“We believe a significant proportion of serious side effects may have genetic origins,” said a Genomics England spokesperson.
“Understanding these patterns can help clinicians make safer, more informed decisions.”
Manufacturer Responses
Both major manufacturers involved in the UK market released statements supporting the investigation.
Eli Lilly, maker of Mounjaro, said:
“Patient safety is our highest priority. Pancreatitis remains an uncommon side effect, and we continuously monitor global safety data.”
Novo Nordisk, which produces Ozempic and Wegovy, said the known risks are clearly listed in product labelling and urged patients to use the drugs only under medical supervision.
Both companies welcomed further research and said they provide ongoing data to health regulators worldwide.
Broader Context: Weight-Loss Jabs Not a Silver Bullet
The launch of this study comes as GLP-1 therapies are increasingly promoted as tools in the fight against the UK’s worsening obesity crisis.However, experts caution they are not a standalone solution, and long-term lifestyle support remains essential.
There is also emerging evidence suggesting some GLP-1 drugs may interfere with the absorption of oral contraceptives, prompting calls for clearer clinical guidance.
The MHRA says the new genetic research will help ensure risks are better understood as usage expands.
