By Amara Osei

The FDA will require warnings for nonarteritic anterior ischemic optic neuropathy (NAION) on all marketed GLP-1 medicines (glucagon-like peptide-1 receptor agonists), including Ozempic, Wegovy, Zepbound, Mounjaro and Eli Lilly’s new pill Foundayo. The class-wide action follows reports of a rare complication that can cause sudden vision loss in one eye and, in some cases, permanent impairment. The FDA said the causes remain incompletely understood, but blood flow to the front of the optic nerve decreases when NAION occurs.

The FDA stated: “NAION cases have been reported for all currently marketed GLP-1 [receptor agonist] products.” Manufacturers must place the warning in the warnings and precautions section of each prescription label, turning a class-level safety signal into standardized information for patients and prescribers.

What does the FDA warning require?

The FDA’s instruction applies across the GLP-1 class, rather than only to the semaglutide products at the center of the 2024 study. The products explicitly named in the agency’s action are:

• Ozempic, Wegovy and Zepbound, alongside Mounjaro and older GLP-1 agonists.
• Foundayo, Eli Lilly’s new GLP-1 pill, which is subject to the same class-wide warning.

Each label must identify the potential risk of sudden vision loss from NAION, including possible permanent impairment. The placement within formal prescribing information gives patients and clinicians a consistent disclosure across diabetes and weight-management medicines.

Why did the FDA act without proof of causation?

FDA scrutiny began after a 2024 study associated semaglutide, a GLP-1 receptor agonist, with NAION among diabetes patients. Its observational design cannot establish causation, but the findings prompted a comprehensive evaluation of clinical trial data, animal data, case reports and other observational studies.

The agency said underlying illnesses complicate the analysis because conditions GLP-1 medicines treat can also increase NAION risk. Its report listed smoking, diabetes, high blood pressure, sleep apnea, anemia and kidney disease as possible risk factors. GLP-1 medicines are prescribed for diabetes and weight management, requiring regulators to distinguish drug effects from those underlying conditions.

Last year, the European Medicines Agency reached a parallel finding from several large epidemiological studies. It wrote: “Results from several large epidemiological studies suggest that exposure to semaglutide in adults with type 2 diabetes is associated with an approximately two-fold increase in the risk of developing NAION compared with people not taking the medicine.”

The EMA recommended a very rare side-effect warning for semaglutide medicines. It estimated that 1 in 10,000 users could be affected.

How large is the vision-loss risk?

The FDA found the risk of vision loss very low but statistically significant enough to report, based on published literature. Its estimate placed NAION incidence in the general population at 2.3 to 10.2 cases per 100,000 people per year among adults older than 50.

Patients who experience sudden, painless changes in vision in one eye should report the symptoms immediately to a health provider. The decision pairs a low population baseline with precaution at the class level, without asserting that GLP-1 medicines caused NAION.

What does broader labeling mean for the market?

The GLP-1 class has been hailed as a modern medical miracle, reflecting its reported use across diabetes, obesity, kidney disease and addiction. As prescriptions broaden, researchers continue to learn how the medicines work and which adverse effects may emerge, a process that could generate additional warning labels in future.

For manufacturers, the immediate obligation is one common NAION disclosure across older agonists, newer products and Eli Lilly’s new pill. For prescribers and patients, the decision supplies consistent language about a rare complication whose absolute population incidence remains low and whose drug association remains under review.

The regulatory strategy combines precaution with evidence limits: class-wide labeling follows the 2024 signal, while the EMA’s roughly twofold estimate and very rare classification set the comparative risk context. The FDA action does not establish causation, but it places a consistent warning on products used across diabetes and weight management before additional evidence resolves the signal.