GLP-1 medicines and NAION: what the new eye warning means

On 9 November 2026 the US Food and Drug Administration (FDA) told every maker of a GLP-1 receptor agonist to add a warning about non-arteritic anterior ischaemic optic neuropathy (NAION) to its prescribing information. NAION is a rare condition in which blood flow to the front of the optic nerve drops, causing sudden, painless loss of vision in one eye that can be permanent. The order covers every product in the FDA's GLP-1 table, including semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity), exenatide, lixisenatide, the combinations Xultophy (liraglutide with insulin degludec) and Soliqua (lixisenatide with insulin glargine), and the oral drug orforglipron (Foundayo).

Short answer: the risk is real enough for regulators on both sides of the Atlantic to act, and small enough that it should not on its own make anyone stop a medicine that is working for them. FDA's analysis of 126 clinical trials found 6.4 cases per 100,000 person-years on GLP-1 medicines against 3.8 on comparators, about 2.6 extra cases for every 100,000 people treated for a year. What matters most is knowing the symptom and acting the same day if it happens.

What NAION is

FDA describes the symptoms as sudden, painless vision loss in one eye that people may notice on waking, blurred or missing areas of vision such as blind spots or tunnel vision, colours looking distorted, and reduced central sharpness. The underlying cause is not fully understood. Risk factors include smoking, diabetes, high blood pressure, sleep apnoea, anaemia and kidney disease, several of which are common in people prescribed GLP-1 medicines. Once one eye has been affected, the risk to the other eye rises. The World Health Organization notes that the vision loss is generally irreversible and that there is currently no effective treatment.

The evidence behind the warning

The concern began with a 2024 study from Massachusetts Eye and Ear in Boston. Among patients seen by one academic neuro-ophthalmology service, those prescribed semaglutide had a much higher rate of NAION: hazard ratios of 4.28 in people with type 2 diabetes and 7.64 in people with overweight or obesity. The patients were drawn from a specialist eye clinic rather than the general population, and the authors said further work was needed to assess causality. FDA said it identified several limitations, but that the study warranted a closer look.

• Clinical trials. FDA pooled 126 randomised trials with 134,253 patients and found 15 probable NAION events: 10 among 78,217 people on GLP-1 medicines, 5 among people given placebo and none among those on other glucose-lowering drugs. The rate was 6.4 cases per 100,000 person-years on GLP-1 medicines and 3.8 on all comparators combined, placebo and other glucose-lowering drugs together. Fifteen events is a small number to base a rate on.
• US real-world data. In FDA's Sentinel study of adults with type 2 diabetes starting treatment between 2019 and 2024, NAION rates were 30 to 32 per 100,000 person-years on GLP-1 medicines, 31 on SGLT-2 inhibitors and 26 on DPP-4 inhibitors. The risk was not significantly higher than with SGLT-2 inhibitors (hazard ratio 1.19, 95% CI 0.91 to 1.54) but was higher than with DPP-4 inhibitors (1.43, 95% CI 1.02 to 2.01).
• A 14-database US network study. Across 37.1 million people with type 2 diabetes, including 810,390 new semaglutide users, the NAION rate among new semaglutide users was 14.5 per 100,000 person-years on the broader case definition and 8.7 on the stricter one. Active-comparator hazard ratios were not significant on the broader definition. The authors still described a modest increase, smaller than first reported, from a self-controlled analysis (incidence rate ratio 1.32, 95% CI 1.14 to 1.54).
• Denmark and Norway. National registries covering 61,377 semaglutide users with type 2 diabetes found a pooled hazard ratio of 2.81 compared with SGLT-2 inhibitors, or about 1.4 extra cases per 10,000 person-years. The authors concluded that the absolute risk remains low.
• Semaglutide or tirzepatide, analysed together. A US records study of 159,398 matched adults with type 2 diabetes compared people prescribed semaglutide or tirzepatide, as one group, with matched people on other diabetes drugs. Over two years, 0.04% (35 of 79,699) developed NAION against 0.02% (19 of 79,699) (hazard ratio 1.76, 95% CI 1.01 to 3.07). The paper does not give a tirzepatide-only hazard ratio.
• Trial meta-analysis for semaglutide. A 2025 review of 78 randomised trials with 73,640 participants found no increase in eye disorders overall, higher odds of NAION (odds ratio 3.92, 95% CI 1.02 to 15.02), and said the evidence was still insufficient for definitive conclusions about NAION.

FDA's review of animal data did not identify a mechanism by which GLP-1 medicines could raise the risk. FDA said that methodologically rigorous observational studies consistently reported an increased risk compared with DPP-4 or SGLT-2 inhibitors, that NAION has been reported for every currently marketed GLP-1 medicine, and that there is a potential increased risk of rare NAION events.

How the US decision compares with Europe and the UK

Europe moved first and more narrowly. In June 2025 the European Medicines Agency's safety committee concluded that NAION is a very rare side effect of semaglutide, meaning it may affect up to 1 in 10,000 people taking it. It estimated about one extra case per 10,000 person-years of treatment in adults with type 2 diabetes, and advised stopping semaglutide if NAION is confirmed. The UK regulator updated its advice for semaglutide in February 2026. Of the European, UK and US actions in this piece, FDA's November 2026 action is the one that covers every GLP-1 medicine on the US market, including tirzepatide and orforglipron. Australia's regulator had already added NAION wording across the GLP-1 medicines sold there on 23 July 2026; that update did not include orforglipron, and the wording for dulaglutide and tirzepatide was narrower than the wording for semaglutide.

These are different estimates, not one figure counted two ways. FDA's 2.6 extra cases per 100,000 person-years is the trial figure across GLP-1 development programmes, which enrolled people with diabetes, obesity and other conditions. The European Medicines Agency's figure, about one extra case per 10,000 person-years, comes from epidemiological studies in adults with type 2 diabetes. The Danish-Norwegian study found about 1.4 extra cases per 10,000 person-years, also in type 2 diabetes. A higher background rate of NAION in type 2 diabetes is one reason the absolute excess can look larger in those studies. That is an explanation of the gap, not a comparison published by FDA or the EMA. Both absolute excesses are in the range regulators describe as rare or very rare.

Our view

• Do not stop a GLP-1 medicine because of this warning on your own. Talk to your prescriber. Regulators have not told people to stop solely because this warning was added. The extra risk in the studies above is about 2.6 cases per 100,000 person-years in the FDA trial analysis, and about 1 to 1.4 cases per 10,000 person-years in the European and Scandinavian type 2 diabetes data. Whether that risk is outweighed by the reason the medicine was prescribed is a decision for you and your prescriber. Some of these medicines, not all of them, also have approved uses to reduce cardiovascular or kidney risk.
• Learn the symptom. Sudden, painless loss or blurring of vision in one eye, often noticed on waking, needs same-day assessment. Do not wait to see whether it clears.
• If you have had NAION before, tell your prescriber. FDA says a history of NAION raises the risk that it will happen in the other eye, and it lists smoking, high blood pressure and sleep apnoea among the risk factors. If a NAION event has occurred, FDA says to discuss whether to continue the medicine or stop it. The FDA text does not single out a dose increase.
• If your GLP-1 medicine comes from an online or private service, tell any eye doctor or emergency clinician you see. It may not appear on your main medical record.
• The FDA order applies to approved GLP-1 products and their prescribing information. Compounded semaglutide or tirzepatide is not that labelled product, so it does not come with the manufacturer's updated warning. Retatrutide is a different, unapproved investigational drug and is not on the FDA's GLP-1 list for this warning; products sold as retatrutide have no approved label.

UK advice

The MHRA's Drug Safety Update of 5 February 2026 says semaglutide may very rarely be associated with NAION. That means it may affect up to 1 in 10,000 people taking it. It tells patients who notice a change in their eyesight, such as sudden blindness, or whose eyesight gets worse very quickly in one or both eyes, to urgently attend eye casualty (if available in the area) or A&E. It asks clinicians to discontinue semaglutide if NAION is confirmed, and reminds them that privately prescribed semaglutide may not appear on a patient's medical record. The MHRA's update covered semaglutide only and said it was reviewing the evidence for other GLP-1 medicines. Up to 1 August 2025 the Yellow Card scheme had received three UK reports suggestive of NAION with semaglutide, against an estimated 10.2 million packs dispensed over five years. Report any suspected side effect through the MHRA Yellow Card scheme.

FAQ

How rare is NAION on GLP-1 medicines?

Rare. FDA's trial analysis found 6.4 cases per 100,000 person-years on GLP-1 medicines against 3.8 on comparators, about 2.6 extra cases per 100,000 person-years. The European Medicines Agency classes NAION as a very rare side effect of semaglutide, meaning it may affect up to 1 in 10,000 people taking it.

Does the warning apply to Mounjaro and Zepbound?

In the US, yes. FDA's order covers every GLP-1 receptor agonist, including tirzepatide and the oral drug orforglipron. The European and UK reviews looked only at semaglutide.

Should I stop my GLP-1 medicine?

Not because of this warning alone, and not on your own. Talk to your prescriber. If NAION is confirmed, the EMA says treatment with semaglutide should be stopped, and the MHRA tells clinicians to discontinue semaglutide. FDA tells prescribers to consider stopping the GLP-1 medicine unless the benefits clearly outweigh the risk, and tells patients to discuss whether to continue or stop. Make that decision with your doctor.

Can NAION be reversed?

The World Health Organization says the vision loss is generally irreversible and there is no effective treatment. That is why acting on symptoms quickly, and telling clinicians about the medicine, matters.