Weight-loss jabs used by millions of Britons have been linked to a surge in suspected “eye stroke” reports – a condition that can destroy sight in one eye for good. Users of the injections have logged 34 suspected cases of the condition, called Naion, with the UK medicines watchdog since 2023. Naion throttles the blood supply to the optic nerve. There is no treatment, and eye experts still cannot fully explain why the fat-fighting jabs might trigger it.
Suspected cases climb sharply
Suspected cases have climbed sharply. For Mounjaro, eye-stroke reports jumped from none in 2024 to 12 in 2025, with eight more logged in the first half of 2026 alone. For semaglutide, the drug in Wegovy and Ozempic, suspected Naion reports have rocketed to 11 so far in 2026, more than the previous three years put together.
The spike follows a blunt safety warning from the Medicines and Healthcare products Regulatory Agency (MHRA) in February, which urged patients to get to A&E fast if their sight suddenly blurs or clouds over.
Expert and regulator comments
Consultant ophthalmologist Samantha Mann said: “An ‘eye stroke’ although untreatable, is exceptionally rare. They are however more common in individuals with risk factors such as diabetes, high blood pressure or high cholesterol, and so it is very hard to say if this cause of blindness is related to the weight-loss injections or not.”
But eye strokes are only the most severe of a wider wave of suspected eye problems now linked to the jabs. In total, users have filed more than 1,000 suspected eye-disorder reports with the MHRA since the drugs took off, 613 for Mounjaro and 406 for semaglutide. For Mounjaro, the reports exploded from 80 in 2024 to 365 in 2025, with a further 168 in the first half of this year.
Other reported eye problems
Blurred vision is by far the most common complaint, logged around 330 times across both drugs. Outright blindness, including cases affecting one eye, has been reported more than 60 times, while dozens more users have described sudden or transient sight loss. Retinal problems, including bleeds, detachments and blocked blood vessels at the back of the eye, account for dozens more suspected reports.
Singer Robbie Williams, 51, has publicly stated he believes the injections have caused his own failing eyesight. Around two million people in Britain are now using some form of weight-loss jab. The MHRA stresses that Naion remains very rare, thought to strike about one in 10,000 people, and that a suspected report is not proof the drug is to blame, with the recent jump partly driven by heightened awareness after its own warning.
Ms Mann said: “Somebody who has an ‘eye stroke’ can wake up and find that they cannot see out of one of their eyes, but these incidents are extremely rare, given the number of people on these weight loss jabs. We also know that these jabs can worsen more advanced diabetic changes at the back of the eye in those known to have diabetes. There are known risks to retinopathy worsening connected to whenever sugar levels drop sharply in the body. The main symptoms that affect the eye tend to be blurring of the vision when reading or black floaters suddenly appearing in the vision that do not disappear. These can be due to swelling or bleeding in the back of the eye. Attending regular eye screening checks or seeing an optometrist can pick up these changes.”
An MHRA spokesperson said: “It is important to place these reports in the context of the millions of GLP-1 prescriptions issued in the UK. Reporting volumes can be influenced by increased use, greater awareness of a potential adverse reaction and other factors. The number of suspected reports should not be taken as the number of confirmed reports or used to work out how often this side effect may occur. As with all medicines, the safety of GLP-1’s are kept under continual review including emerging evidence from spontaneous data and scientific publications. If you notice a change in your eyesight, such as sudden blindness or your eyesight gets worse very quickly in one or both of your eyes during treatment with semaglutide, urgently attend eye casualty (if available in your area) or A&E. On the basis of the current evidence, the benefits of GLP-1 receptor agonists outweigh the potential risks when used in line with their authorised uses.”
Manufacturers respond
Mounjaro’s manufacturers said: “Patient safety is Lilly’s top priority. We actively monitor, evaluate, and report safety information for all our medicines to the MHRA and encourage healthcare professionals and others to do so via the MHRA Yellow Card adverse event reporting process. Recent literature has concluded that the ‘evidence does not establish a causal relationship between GLP-1RAs and Naion’.”
Novo Nordisk, who produce Wegovy and Ozempic, said: “Patient safety is our top priority, and we take any reports about adverse events from the use of our medicines very seriously. We work closely with authorities and regulatory bodies from around the world to continuously monitor the safety profile of our products. Based on the totality of evidence we concluded that the data did not suggest a reasonable possibility of a causal relationship between semaglutide and Naion, and Novo Nordisk believes that the benefit-risk profile of semaglutide remains favourable.”
