.png "Global Insight")
The world's most popular weight-loss and diabetes drugs are getting a new warning — about eyesight. On Monday, the US Food and Drug Administration told the makers of every GLP-1 drug, including Ozempic, Wegovy, Mounjaro and Zepbound, that they must warn patients about a rare eye condition that can cause sudden, permanent vision loss. The condition is called NAION, and while the risk is small, the FDA says the evidence is now strong enough that patients and doctors need to know about it.
NAION — non-arteritic anterior ischemic optic neuropathy — happens when blood flow to the front of the optic nerve suddenly drops. The FDA describes it as a rare condition that can cause acute, painless, decreased vision in one eye, including permanent vision loss. Its underlying cause is not completely understood, but smoking, diabetes, high blood pressure, sleep apnoea, anaemia and kidney disease are all listed as possible risk factors. It is sometimes called an "eye stroke", and it usually strikes without pain — often noticed first thing in the morning.
What the FDA actually found
The FDA's review began after a July 2024 study in JAMA Ophthalmology linked the diabetes drug semaglutide to a higher rate of NAION. The agency then examined clinical trial data, animal studies, post-marketing reports, observational studies and its own real-world evidence. Pooling 126 randomised controlled trials covering 134,253 patients, it found 15 probable NAION cases — 10 among patients taking GLP-1 drugs and five among those on a placebo. The rate worked out at 6.4 cases per 100,000 person-years for GLP-1 users, against 3.8 per 100,000 in comparison groups. A large 2025 study tracking nearly 175,000 diabetic patients on semaglutide found the risk of NAION more than doubled after two years of treatment.
Crucially, the FDA did not conclude that GLP-1 drugs cause NAION. Its wording is careful: there is a "potential increased risk". That distinction matters, and the drugmakers are leaning on it. Novo Nordisk, which makes Ozempic and Wegovy, told CNN that it "continues to believe the data do not establish a cause-and-effect relationship". Eli Lilly, maker of Mounjaro and Zepbound, noted that the FDA communication "applies to all medicines with GLP-1 RA activity and does not reference any findings specific to Lilly medicines". Dozens of lawsuits have already been filed against both companies by patients who say the drugs damaged their eyesight.
Why the warning is coming now
The United States is catching up with regulators elsewhere. Last year, the European Medicines Agency said NAION may affect up to 1 in 10,000 people taking semaglutide for at least a year, and warnings have been on European labels since June. They are already present in the United Kingdom, Denmark and Australia. In Denmark, four patients who lost vision after using Novo's GLP-1 drugs were granted compensation last year. The FDA order covers the entire class — a dozen drugs approved since 2005, from semaglutide and tirzepatide to liraglutide, dulaglutide and the newly approved orforglipron — because NAION cases have been reported with every GLP-1 product on the market.
For patients, the practical advice is straightforward. Anyone taking a GLP-1 drug should report sudden, painless vision loss in one eye, blurred or missing parts of vision, blind spots, colour distortion or reduced central sharpness to their doctor right away — and doctors are now told to send such patients to an eye specialist. The absolute risk remains very low: even at the FDA's figures, it is a handful of extra cases per 100,000 people treated. But for a drug class taken by millions, a rare risk is still a risk worth naming on the label. This article is general information only and is not medical advice.
Sources: CNN; USA Today. The FDA has identified a potential increased risk, not a proven cause-and-effect relationship.