The United States Food and Drug Administration (FDA) has directed manufacturers of popular diabetes and weight-loss medications to update their product labels to include warnings about a rare eye condition that could cause sudden vision loss.

The directive affects drugs belonging to the GLP-1 medication class, including Ozempic and Wegovy, produced by Novo Nordisk, as well as Eli Lilly’s Mounjaro and Zepbound.

According to the FDA, the updated labels must highlight the possible risk of non-arteritic anterior ischemic optic neuropathy (NAION), a condition that occurs when blood supply to the front part of the optic nerve is reduced.

NAION can cause sudden and painless loss of vision. Although the condition is uncommon, some affected individuals may experience permanent damage to their eyesight.

The regulator said its decision followed an assessment of available evidence, including clinical trial results, animal studies, reports from patients and observational research.

Reacting to the development, Eli Lilly said it was reviewing the FDA’s latest communication and would respond to the agency. The pharmaceutical company also stressed that the warning was not based on findings specifically linked to its medications.

Novo Nordisk, on its part, maintained that available evidence had not established a direct cause-and-effect relationship between its GLP-1 drugs and the eye condition. The company also expressed confidence in the overall benefits and safety profile of its medications.

Concerns about the possible connection are not entirely new. In June 2025, the European Medicines Agency’s safety committee identified NAION as a potential side effect of semaglutide, the active ingredient in Ozempic and Wegovy, estimating that it could affect up to one in 10,000 users.

Further concerns emerged from a 2025 study involving nearly 350,000 people with diabetes. Researchers found that patients treated with semaglutide had more than twice the risk of developing NAION after two years compared with those taking other classes of diabetes medication.

Despite the warning, analysts believe the relatively low occurrence of the condition and the established benefits of GLP-1 medications in managing diabetes, obesity and other health risks are unlikely to significantly change their use.