The GLP-1 warning ordered by the Food and Drug Administration on Monday will put a new risk on the labels of the world’s most widely used weight loss and diabetes drugs. The agency told the makers of all GLP-1 medicines, including Ozempic, Wegovy, Mounjaro and Zepbound, to add a warning about a rare eye condition that can cause sudden and sometimes permanent vision loss. The condition, non-arteritic anterior ischemic optic neuropathy, known as NAION, is caused by reduced blood flow to the optic nerve. The FDA said the GLP-1 warning will go in the warnings and precautions section of every GLP-1 label.
The GLP-1 warning covers a condition that usually shows up as sudden, painless vision loss in one eye, which some people first notice on waking. The loss can be permanent. The FDA said the underlying cause is not completely understood, and its review of animal data found no mechanism for how the drugs could raise the risk. Symptoms listed by the agency include blurred vision, blind spots, distorted colours and other visual disturbances. The FDA urged patients who notice such problems to contact a health care professional at once. The agency did not tell patients to stop taking their medicine.
GLP-1 warning and the numbers behind it
The GLP-1 warning rests on an FDA analysis of more than 125 clinical trials involving over 134,000 patients. Across those trials, the agency found 15 probable cases of NAION: 10 among 78,217 patients on a GLP-1 drug and five among 56,036 patients on a placebo or other diabetes drug. That works out to 6.4 cases per 100,000 patients treated with a GLP-1 for a year, against 3.8 per 100,000 in comparison groups. The gap is about 2.6 extra cases per 100,000 person years. The FDA also reviewed its adverse event database and observational studies before deciding.
The GLP-1 warning follows a review that began after researchers at Mass Eye and Ear reported in July 2024 that patients prescribed semaglutide were more likely to develop NAION than those not taking the drug. Their findings were published in JAMA Ophthalmology, a journal of the American Medical Association. Semaglutide is the active ingredient in Ozempic and Wegovy. The FDA listed NAION with GLP-1 drugs as a potential signal of a serious risk in its October to December 2024 quarterly report. Europe moved first: the European Medicines Agency said in June 2025 that NAION was a very rare side effect of semaglutide, and Britain, Japan and Australia already require similar warnings.
Drugmakers respond to the GLP-1 warning
Drugmakers are weighing how to answer the GLP-1 warning. Eli Lilly, which makes Mounjaro and Zepbound, said it is carefully evaluating the update and will respond to the FDA promptly. Novo Nordisk, which makes Ozempic and Wegovy, denied part of the FDA’s account, according to NBC News, which first reported the order. The warning applies to a dozen GLP-1 drugs approved since 2005, including Novo Nordisk’s Rybelsus, Victoza, Saxenda and Xultophy, and Eli Lilly’s Trulicity. Makers could still challenge the order, but the final decision on the labeling rests with the agency.
The GLP-1 warning also lands while lawsuits over vision loss are moving through the courts. Dozens of cases have been filed in state and federal courts against Lilly and Novo Nordisk by patients who say the drugs permanently damaged their eyesight. As of October, 247 vision loss cases were pending in federal court, where they were brought together as multidistrict litigation in the Eastern District of Pennsylvania. The FDA said its review covered clinical trial data, animal data and post marketing reports, including case reports and observational studies.
The GLP-1 warning does not change the advice for patients who take the drugs. The FDA said the risk is rare, and the warning is meant to make sure patients and doctors know about it and act fast if vision changes. Anyone who notices sudden changes in vision should contact a doctor promptly rather than waiting for the next scheduled visit. The agency said it will keep watching reports of NAION as the new labels reach pharmacies.