Obesity medication and the risk of sudden vision loss (NAION) according to the EMA and FDA

NAION is a very rare but serious eye condition: because of a reduced blood supply to the optic nerve, vision in one eye gets worse suddenly and without pain.

On 9 November 2026, the US Food and Drug Administration (FDA) required the manufacturers of all GLP-1 medicines available in the US, including tirzepatide (Mounjaro), to add a warning about a possible increased risk of NAION to the product information (1). The European Medicines Agency (EMA) had already concluded in June 2025 that NAION is a very rare side effect of semaglutide, the active substance in Wegovy, Ozempic and Rybelsus. It may affect up to 1 in 10,000 people taking semaglutide (2). In Poland, the summaries of product characteristics (SmPCs) and patient leaflets approved in the European Union apply. The NAION warning has been added to the product information for semaglutide, but not for tirzepatide (3, 4).

With any obesity medicine, sudden loss of vision or rapidly worsening vision in one eye needs immediate medical help.

In brief

• NAION is rare: each year it affects about 2-10 in 100,000 people over the age of 50. There is no treatment with proven effectiveness, and in about three in five patients sharpness of vision (visual acuity) does not improve (1, 5).
• The EMA has recognised NAION as a very rare side effect of semaglutide. In people with type 2 diabetes, this means roughly one additional case per 10,000 people treated for a year. This figure cannot be applied to tirzepatide or to other medicines.
• The FDA's warning covers all GLP-1 medicines, including tirzepatide, but it describes the risk as possible and does not state that these medicines cause NAION.
• Sudden, painless loss of vision in one eye, dark spots in your field of vision or blurred vision need immediate help. The EMA and FDA do not advise people without such symptoms to stop taking their medicine.

What is NAION and why can vision loss be permanent?

NAION is a reduced blood supply (ischaemia) to the optic nerve at the point where the nerve enters the eyeball. When less blood reaches this part of the nerve, the nerve swells and presses on its own nerve fibres. The compressed fibres die, and the person partly loses vision in that eye (1, 5). NAION stands for non-arteritic anterior ischaemic optic neuropathy. Its Polish name is nietętnicza przednia niedokrwienna neuropatia nerwu wzrokowego (3).

In adults, NAION is the second most common cause, after glaucoma, of permanent vision loss due to optic nerve damage. Even so, it remains a rare condition: each year it is diagnosed in 2.3-10.2 per 100,000 people over the age of 50 (1, 5). There is no treatment with proven effectiveness, and in about three in five patients visual acuity does not improve. A prompt examination is also needed because the doctor has to rule out other causes of vision loss that need urgent treatment, such as a stroke (5).

NAION symptoms that need immediate help

The FDA lists the symptoms that should prompt a patient taking a GLP-1 medicine to contact a doctor straight away (1):

• sudden, painless loss of vision in one eye, often noticed on waking
• dark spots in the field of vision, or tunnel vision
• changes in how colours look
• blurred or hazy vision in the centre of the field of vision

What should you do if your vision suddenly gets worse during obesity treatment?

Sudden worsening of vision in one eye needs immediate medical help and an eye examination (3). If you cannot get an urgent appointment with an ophthalmologist, go to a hospital with an ophthalmology department. Tell the doctor which obesity medicine you take, at what dose and when you started it.

How do the EMA and FDA decisions on NAION differ?

The EMA assessed a single substance, semaglutide, and recognised NAION as a very rare side effect of it. The FDA's warning covers the whole group of GLP-1 medicines, but it calls the risk possible (1, 2). In Poland, medicines are sold with SmPCs and patient leaflets approved in the European Union, so the FDA decision does not change the leaflets in Polish pharmacies.

The EMA and FDA figures describe different measures in different groups of people, so they should not be compared directly. The EMA figure shows how many more cases of NAION were seen in patients taking semaglutide, while the FDA figure shows how often NAION was diagnosed in trials of all GLP-1 medicines (1, 2).

What did the EMA decide about semaglutide in 2025?

On 6 June 2025, the EMA's safety committee (PRAC) completed its review of semaglutide medicines. The committee analysed animal studies, clinical trials, reports of side effects after the medicines came onto the market, and the medical literature. It concluded that NAION is a very rare side effect of semaglutide that may affect up to 1 in 10,000 people taking it (2).

Several large epidemiological studies indicate that in adults with type 2 diabetes taking semaglutide, the risk of NAION is roughly twice as high as in people not taking it. In absolute terms, this is roughly one additional case per 10,000 people treated for a year, or per 5,000 people treated for two years (2, 3). This estimate comes from studies of people with type 2 diabetes, and the EMA press release gives no separate figure for people with obesity who do not have diabetes. Clinical trials also pointed to a slightly higher risk in people taking semaglutide than in those given a placebo (2).

After this assessment, NAION was added to the SmPCs and patient leaflets of semaglutide medicines. In the Wegovy SmPC, the warning covers both the injections and the tablets. The document also states that it is not known how long after the start of treatment NAION may develop. If NAION is confirmed by an eye examination, semaglutide is stopped (3).

What NAION warning did the FDA introduce in November 2026?

On 9 November 2026, the FDA published a drug safety communication on GLP-1 medicines, also known as GLP-1 receptor agonists. All manufacturers of these medicines in the US must add information about a possible increased risk of NAION to the Warnings and Precautions section of the prescribing information for doctors. The FDA's list includes, among others, semaglutide (Ozempic, Rybelsus, Wegovy), tirzepatide (Mounjaro, Zepbound), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity) and orforglipron, which was approved in the US in 2026 (1).

The FDA based its decision on three types of data (1):

• Clinical trials: in 126 trials involving 134,253 patients, probable NAION occurred in 10 people taking GLP-1 medicines and in 5 people in comparison groups, which works out at 6.4 compared with 3.8 cases per 100,000 people per year.
• The US Sentinel database: among adults with type 2 diabetes who started a GLP-1 medicine, an SGLT-2 inhibitor or a DPP-4 inhibitor between 2019 and 2024, the risk of NAION with GLP-1 medicines was about 43% higher than with DPP-4 inhibitors. Compared with SGLT-2 inhibitors, the difference was not statistically significant.
• Published observational studies: the best-designed of them consistently showed a higher risk of NAION with GLP-1 medicines than with DPP-4 or SGLT-2 inhibitors in people with type 2 diabetes.

The FDA refers to a possible increase in the risk of NAION. It has not concluded that GLP-1 medicines cause NAION. Animal studies found no mechanism that would explain such an effect, and side effect reports are hard to assess because many patients treated with these medicines have diabetes, high blood pressure and other risk factors for NAION. Cases of NAION have been reported with all GLP-1 medicines available in the US (1).

The FDA advises doctors to tell patients about the symptoms of NAION, to refer a patient to an ophthalmologist straight away if NAION is suspected, and, once NAION is diagnosed, to consider stopping the GLP-1 medicine unless the benefits of treatment clearly outweigh the risks (1).

Does the NAION warning apply to people taking Mounjaro?

The EU-approved product information for Mounjaro (as of November 2026) does not list NAION among its warnings or side effects, whereas in the US the FDA requires this warning for tirzepatide as well (1, 4). The EU product information for Saxenda (liraglutide) does not mention NAION either (6). The fact that NAION is not listed does not mean that tirzepatide definitely does not increase the risk. Most of the research concerns semaglutide. For tirzepatide and the other medicines in this group, studies either do not point to an increased risk or give results that are inconclusive or weaker than for semaglutide (7). The authors of a review published in 2026 in the Journal of the Endocrine Society consider the available data insufficient to conclude that an increased risk of NAION applies to the whole group of GLP-1 medicines (5).

The figure of 1 in 10,000 people treated for a year cannot be applied to tirzepatide either. The EMA estimate concerns semaglutide in people with type 2 diabetes, and the FDA's clinical trial data cover all GLP-1 medicines combined and do not show the risk for each medicine separately (1, 2). The symptoms of NAION, however, are the same whatever the medicine. Someone taking Mounjaro whose vision in one eye suddenly gets worse needs immediate help just as much as someone taking Wegovy.

Who is at higher risk of NAION?

NAION mainly affects people over the age of 50 and people with blood vessel disease (1, 5). The FDA lists smoking, diabetes, high blood pressure, sleep apnoea, anaemia and kidney disease as risk factors (1). The factor most strongly linked to NAION is the structure of the eye: in 60-80% of patients, the optic disc (the point where the nerve enters the eyeball) is small and crowded, with only a small cup (hollow) in the centre. An ophthalmologist assesses this during an examination of the back of the eye (fundus examination) (5).

Many of these conditions go hand in hand with obesity, so some people treated for obesity have a higher risk of NAION regardless of the medicine. This also makes study results hard to interpret, because it is not easy to tell how many cases of NAION are due to the medicine and how many to the conditions for which the patient was prescribed it (1, 5).

Someone who has had NAION in one eye has a higher risk that the condition will affect the other eye or come back (1). According to the authors of the 2026 review in the Journal of the Endocrine Society, people who have had NAION are not good candidates for treatment with GLP-1 medicines (5).

Where did the headlines about vision loss after obesity medication come from?

The first warnings came from a study published in 2024 in JAMA Ophthalmology. The researchers analysed the records of patients at a single neuro-ophthalmology centre. Among people with overweight or obesity who were prescribed semaglutide, NAION was diagnosed within 3 years in 6.7%, compared with 0.8% in the group treated with other obesity medicines (8). Such high percentages may reflect the fact that a neuro-ophthalmology centre sees patients referred by other doctors, whose risk of optic nerve disease is higher than average (5).

In later, much larger studies, the increase in risk was smaller. In an analysis of data on 37.1 million people with type 2 diabetes from 14 databases, NAION was diagnosed in 14.5 per 100,000 people treated with semaglutide for a year, and the authors rated the increase in risk as moderate, smaller than in the first study (9). Some studies found no increased risk. In the others, according to the 2026 review, the risk was 1.2 to 4.3 times higher than without GLP-1 medicines, with the highest values coming from the first study at the neuro-ophthalmology centre (5).

What should you tell your doctor before starting obesity treatment?

Tell the doctor assessing you for treatment if you have had NAION or any other eye condition, including diabetic retinopathy, and if you have sleep apnoea or kidney disease, or smoke. The EMA and FDA communications do not recommend an eye examination for every patient before starting treatment (1, 2). The authors of the Journal of the Endocrine Society review suggest that the doctor should consider referring people with several risk factors for NAION to an ophthalmologist. People with diabetes should have the back of the eye examined every year anyway, and at that visit the ophthalmologist can assess the structure of the optic disc (5). People with diabetic retinopathy who are treated with semaglutide need close monitoring by an ophthalmologist (3).

How the assessment for treatment works is explained in our article on when a doctor will prescribe obesity medication, and the tests ordered at the start are described in our article on tests before obesity treatment.

Do you need to stop obesity medication because of the NAION warnings?

If your vision is fine, you do not need to stop your medicine because of the NAION warnings. The EMA and FDA communications do not recommend stopping treatment in people whose vision has not got worse. They describe how to recognise the symptoms of NAION and what to do if they appear (1, 2). The same 2026 review recommends treating the link between GLP-1 medicines and NAION as a safety signal, not as a contraindication to treatment (5).

Stopping the medicine on your own has consequences: in most people, body weight starts to go up after treatment ends. We describe this in our article on stopping obesity medication. Other symptoms that need urgent help during obesity treatment are covered in our article on side effects of obesity medication.

Once NAION has been diagnosed, the situation is different. Semaglutide is then stopped (3). The FDA advises doctors to consider stopping any GLP-1 medicine unless the benefits of treatment clearly outweigh the risks (1). Decisions about further obesity treatment are made by a doctor who knows the result of the eye examination.

In the obesity treatment programme at Nasz Gabinet, the doctor prescribes semaglutide (Wegovy as injections or tablets) or tirzepatide (Mounjaro) and reviews your measurements from the app every month. Report any change in your vision during treatment to the doctor in charge of your treatment. If your vision suddenly fails, get immediate medical help first. This article does not replace a consultation with a doctor who knows your medical conditions and the medicines you take.

Frequently asked questions

Can Ozempic also cause NAION?

Yes, in very rare cases. Ozempic contains semaglutide, the same substance as Wegovy, but it is licensed for treating type 2 diabetes. The EMA decision of June 2025 covered Ozempic, Wegovy and Rybelsus (2).

Do Wegovy tablets also carry a NAION warning?

Yes. In the European Wegovy SmPC, the NAION warning and the entry among very rare side effects apply to both the injections and the semaglutide tablets (3).

Does stopping the medicine bring back vision lost to NAION?

The EMA and FDA communications do not say that stopping the medicine restores vision. The FDA points out that vision loss from NAION can be permanent (1). There is no treatment for NAION with proven effectiveness, and in about three in five patients visual acuity does not improve (5).

Does any worsening of vision during obesity treatment mean NAION?

No. In people with diabetes who have diabetic retinopathy, a rapid improvement in blood sugar can temporarily make the changes in the retina worse and affect vision (3). The cause is established by an ophthalmologist during an examination. Sudden worsening of vision in one eye needs immediate help. Problems with your eyesight that build up gradually should be reported to the doctor in charge of your obesity treatment (3).

Sources

1. U.S. Food and Drug Administration. FDA requires safety labeling changes for glucagon-like peptide-1 receptor agonists (GLP-1 RAs) due to potential increased risk of rare but serious eye condition. Drug Safety Communication, 9.11.2026. fda.gov
2. European Medicines Agency. PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy. Press release, 6.06.2025. ema.europa.eu
3. European Medicines Agency. Wegovy (semaglutyd), roztwór do wstrzykiwań i tabletki - charakterystyka produktu leczniczego i ulotka dla pacjenta (solution for injection and tablets, summary of product characteristics and patient leaflet), sections 4.4 and 4.8. ema.europa.eu
4. European Medicines Agency. Mounjaro (tirzepatyd) - charakterystyka produktu leczniczego i ulotka dla pacjenta (summary of product characteristics and patient leaflet). ema.europa.eu
5. Ruan F, Gnana B, Mei C et al. Current review of glucagon-like peptide 1 receptor agonists and risk of nonarteritic anterior ischemic optic neuropathy. J Endocr Soc. 2026;10(11):bvag224. PMID 42857401, DOI
6. European Medicines Agency. Saxenda (liraglutyd) - charakterystyka produktu leczniczego i ulotka dla pacjenta (summary of product characteristics and patient leaflet). ema.europa.eu
7. Malluhi M, Al-Naemi A, Akhtar S. GLP-1 receptor agonists and ocular safety - pharmacokinetic insights into ischemic optic neuropathy and diabetic retinopathy risk: a review. Biomol Biomed. 2026. PMID 42770962, DOI
8. Hathaway JT, Shah MP, Hathaway DB et al. Risk of nonarteritic anterior ischemic optic neuropathy in patients prescribed semaglutide. JAMA Ophthalmol. 2024;142(8):732-739. PMID 38958939, DOI
9. Cai CX, Hribar M, Baxter S et al. Semaglutide and nonarteritic anterior ischemic optic neuropathy. JAMA Ophthalmol. 2025;143(4):304-314. PMID 39976940, DOI