A new and concerning study published in the British Journal of Ophthalmology has revealed a significant link between GLP-1 weight loss medications and an increased risk of permanent sight loss, specifically ischemic optic neuropathy (ION), often referred to as an 'eye stroke'. The study found that users of Wegovy, a popular weight loss jab containing the powerful ingredient semaglutide, face five times the risk of this condition compared to those taking other GLP-1 medications. Furthermore, men were found to have a three times greater risk than women.

Ischemic optic neuropathy occurs when blood flow to the optic nerve is restricted, depriving it of oxygen and leading to sudden and often permanent vision loss. While experts have previously debated the prevalence of this issue among weight loss drug users, with manufacturers initially stating that blindness was not a 'known adverse drug reaction', this new research provides crucial insights. Canadian experts meticulously analyzed reports of harmful side effects associated with GLP-1 drugs submitted to the US Food and Drug Administration (FDA) between December 2017 and 2024 to pinpoint the risk associated with specific medications.

The study's findings are the first to demonstrate a formulation-and-dose-dependent ION risk, with the strongest association clearly observed for Wegovy. Researchers examined eye-strokes linked to various semaglutide-containing drugs, including up to 2mg of Ozempic for type 2 diabetes, 2.4mg of Wegovy for obesity, and the daily oral pill Rybelsus for type 2 diabetes. They also included reports for tirzepatide, sold as Mounjaro, for type 2 diabetes.

Out of over 30 million adverse event reports analyzed, more than 31,000 involved semaglutide users, primarily women aged around 56. Despite Ozempic generating approximately seven times more reports of harmful side effects overall due to its earlier approval, ION was reported an astonishing 75 times more frequently by individuals taking Wegovy. Interestingly, no link was found between Rybelsus and sudden vision loss.

The researchers theorize that higher doses of Wegovy may reduce blood flow to the optic nerve by causing a sudden drop in blood pressure. In contrast, Rybelsus is absorbed much more slowly, which could minimize the risk of such a rapid blood pressure reduction. They emphasize that these findings add to a growing body of literature reporting ocular complications with anti-obesity medications, necessitating urgent scrutiny and clarification for ophthalmologists, especially given the increasing use of these jabs in children, which could elevate their risk of vision problems later in life.

Following these concerns, the Medicine's and Healthcare products Regulatory Agency (MHRA) in the UK issued a warning last month, urging weight loss jab users to report any changes in their vision to a medical professional. They advised patients taking semaglutide who experience a sudden impairment or rapid worsening of eyesight in one or both eyes to urgently attend eye casualty or A&E. Consequently, Wegovy prescriptions in the UK will now include a safety warning about the risk of blindness. Since semaglutide was authorized in the UK in 2018, there have been three suspected reports of eye-stroke out of an approximate 10.2 million prescriptions issued.

Estimates from UCL suggest that up to 1.6 million people in Britain have used weight-loss drugs like Wegovy or Mounjaro in the past year, with usage doubling between 2024 and 2025, primarily through private access rather than the NHS. Ischemic optic neuropathy currently has no known treatments, and vision often does not improve; it is thought to affect approximately one in 10,000 people. Celebrities like Robbie Williams have also voiced concerns about the vision risks associated with weight loss jabs.

Novo Nordisk, the developer of semaglutide, is currently facing several lawsuits in the US from patients alleging sight loss. In their response, Novo Nordisk affirmed that patient safety is their top priority, and they diligently monitor the safety profile of their products in collaboration with authorities. While they believe the totality of evidence does not suggest a reasonable possibility of a causal relationship between semaglutide and ION, and that the benefit-risk profile remains favorable, they have updated the EU patient leaflets and Summary of Product Characteristics for Wegovy, Ozempic, and Rybelsus to include the risk.