Patients using obesity medications in the United Kingdom have submitted nearly 150,000 reports of adverse side effects, with more than 150 deaths potentially linked to these drugs, according to data from the Medicines and Healthcare Products Regulatory Agency (MHRA). The reports concern several GLP-1 receptor agonist medications prescribed through the National Health Service (NHS), including liraglutide (Saxenda), semaglutide (Wegovy), and tirzepatide (Mounjaro).

Data collected via the MHRA’s Yellow Card scheme, which allows patients and healthcare professionals to report suspected side effects, indicates that tirzepatide accounts for the majority of reports. Over 100,000 adverse reaction reports were connected to tirzepatide, about 10,000 of which were classified as serious, with the MHRA linking the drug to 98 deaths. Eli Lilly, the manufacturer of Mounjaro, confirmed that global sales of tirzepatide have doubled this year.

For liraglutide, some 3,000 adverse reaction reports were recorded, including 734 deemed serious, with 18 associated deaths. Semaglutide had around 44,000 adverse reaction reports, 4,800 of them serious, and 37 deaths potentially linked to its use.

The MHRA cautions that the number of reports does not necessarily represent individual patients, as multiple reports can be filed per person. Additionally, fatal outcomes may result from underlying or undiagnosed health conditions rather than the medications themselves. The Yellow Card scheme accepts reports from patients, relatives, and medical professionals who suspect a link between the medication and adverse events, though these remain unverified causal associations.

Concerns have been raised over the safety profile of these medications following recent inquests into deaths potentially connected to their use. In Norfolk, a coroner is investigating the death of a 73-year-old woman in 2024 after she increased her Mounjaro dosage. Similarly, in Devon and Plymouth, an inquest has been initiated into the death of Paula Owen, 66, who passed away on July 23, with preliminary findings suggesting a GLP-1 agonist medication may have played a role.

In response to growing safety concerns, the MHRA updated its product information in January 2026, highlighting risks of severe pancreatitis—including necrotising and fatal cases—following a rise in such reports to the Yellow Card scheme.

The developments come amid multiple lawsuits filed in the United States against Novo Nordisk and Eli Lilly, the manufacturers of these weight-loss drugs. Representatives from both companies underscored their commitment to patient safety. Novo Nordisk emphasized the importance of prescribing and using these medications under healthcare professional supervision, noting that side effects vary among individuals. Eli Lilly stated that it actively monitors and reports safety information to ensure patient well-being.