Leading GLP-1 receptor agonist drugs, widely used for diabetes and weight management, are currently under fresh scrutiny regarding a potential link to a rare eye condition known as non-arteritic anterior ischaemic optic neuropathy (NAION). This condition, which disrupts blood flow to the optic nerve, can lead to sudden, painless vision loss, typically in one eye.
Regulatory Actions and Conflicting Evidence
Danish drugmaker Novo, a key producer of GLP-1 medicines, recently acknowledged data from its own clinical trials which recorded instances of NAION among participants. This statement follows real-world patient studies suggesting an association between semaglutide, a prominent GLP-1 drug, and the eye condition.
However, Novo maintains that a pooled analysis of its extensive randomized clinical trials involving both liraglutide and semaglutide, covering over 96,000 individuals, did not show an increased incidence of NAION among those receiving GLP-1 medicines compared to inactive treatments. The company cited only three confirmed NAION cases in the GLP-1 arm versus five in the control group.
Conversely, evidence from routine clinical practice has been less consistent. A 2026 meta-analysis of observational studies indicated a higher risk of NAION with semaglutide use, while other reviews found no statistically significant overall increase, rating the evidence certainty as low to very low.
European Regulators Issue Warning
The European Medicines Agency (EMA) has taken a decisive regulatory stance. In June 2025, its safety committee classified NAION as a very rare side effect of semaglutide, estimating it could affect up to one in 10,000 users. The EMA noted that several large epidemiological studies suggested adults with type II diabetes taking semaglutide had approximately twice the risk of developing NAION compared to non-users.
Consequently, the EMA recommended updating product information for semaglutide medicines. Patients experiencing sudden vision loss or rapidly worsening eyesight are advised to contact their doctor immediately, and treatment should be discontinued if NAION is confirmed.
US Litigation and Market Impact
The issue has also escalated into US courts, with federal cases consolidated into a multidistrict litigation in Pennsylvania. This involves products from both Novo and Eli Lilly, including Novo’s Ozempic and Wegovy, and Lilly’s Trulicity. Plaintiffs allege that the use of these GLP-1 medicines caused NAION, raising common issues regarding the drugs’ development, testing, regulatory history, promotion, and labeling.
As of September 1, 2026, 216 actions were pending in this multidistrict litigation. It is important to note that this consolidation is a procedural step and does not establish causation between the medicines and the eye condition.
The litigation emerges as Novo and Lilly dominate the rapidly expanding market for metabolic drugs. Their blockbuster GLP-1 and GIP/GLP-1 agonist brands, such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), are significant revenue drivers.
In India, the GLP-1 market has expanded significantly, reaching ₹2,333 crore by August 2026. With Novo’s semaglutide patent expiring, several domestic pharmaceutical companies have launched generic versions, broadening the number of entities exposed to developments concerning the drug’s safety profile.
Despite the ongoing scrutiny and litigation, Novo Nordisk asserts that, considering all available evidence from trials, post-marketing reports, and observational studies, alongside the generally low incidence rate of NAION, the benefit-risk profile of semaglutide remains favorable.