The answer so far
Semaglutide has been linked to a very rare optic-nerve condition called NAION. Sudden vision loss, including partial loss, or rapidly worsening eyesight needs urgent eye-emergency or emergency-department assessment, even if there is no pain. Tell the care team about all medicines; these symptoms can have other causes too.12
On this page
Semaglutide and vision loss: what is NAION? Choose a step to explore this subject in more detail.
Urgent first step: sudden vision change
The UK medicines regulator advises people taking semaglutide to attend an eye emergency service or emergency department urgently if vision is suddenly lost, partly lost or rapidly deteriorates. NAION is often painless, but absence of pain does not make sudden vision loss harmless. Other conditions can cause similar symptoms and also need assessment. Tell the team the exact medicines you take, even if they were prescribed privately. The regulator advises clinicians to discontinue semaglutide if NAION is confirmed; seek assessment rather than trying to diagnose the cause yourself.1
- NAIONReduced blood flow damages the optic nerve; vision loss is often sudden and painless.
- Diabetic retinopathyDiabetes can damage blood vessels in the retina; early disease may have no symptoms.
- Different evidenceThe rare NAION warning and the SUSTAIN-6 retinopathy findings describe different conditions and studies.
- What to tell the teamShare the exact medicine, any eye diagnosis, previous treatment and changes in sight.
What is NAION, and is it diabetic retinopathy?
NAION means non-arteritic anterior ischaemic optic neuropathy: reduced blood flow damages the front of the optic nerve, which carries visual information from the eye to the brain. It usually affects one eye at a time and can cause sudden, painless cloudy or lost vision. Diabetic retinopathy is different: it affects blood vessels in the light-sensitive retina at the back of the eye. Its early stages can have no symptoms. For that separate question, read semaglutide and diabetic retinopathy.14
How rare is the warning?
In 2025 the European Medicines Agency concluded that NAION is a very rare side effect of semaglutide medicines; its frequency category means it may affect up to one in 10,000 people. The UK MHRA describes a very rare association. It cites a European review suggesting roughly one additional case per 10,000 people treated per year among adults with type 2 diabetes. The side-effect category and an estimated extra annual case rate are different measures, not two figures to add together. Neither predicts an individual outcome.12
What did a large US study find?
Researchers studied 102,361 US veterans with type 2 diabetes on metformin who began semaglutide or another diabetes-drug class called SGLT2 inhibitors. Median follow-up was 2.1 years. In a statistical analysis that balanced measured characteristics, estimated occurrence of NAION was 0.29% among semaglutide starters and 0.13% among comparison-drug starters. Most participants were men. Treatment was not randomly assigned, so differences in health, diagnosis and other factors could still affect the comparison. These estimates concern that study and population, not everyone taking semaglutide; they are not directly interchangeable with the UK regulator’s annual estimate.3
Does a link mean the medicine caused every case?
No. NAION can happen without semaglutide, and type 2 diabetes itself is associated with higher risk. Studies compare groups but cannot determine the cause of an individual case. The biological explanation and risk in different groups remain under study. A report of a suspected side effect alone does not establish that the medicine caused it. At the same time, the regulator warning is a reason to recognise symptoms and seek prompt assessment.123
What about the medicine’s benefits?
Semaglutide is used for different purposes in different people. In the SELECT trial, adults with established cardiovascular disease and overweight or obesity, but without diabetes, had fewer major cardiovascular events on average with the studied weekly semaglutide injection than placebo. That is a different population and outcome from the eye studies. Benefits and harms should be considered together with the prescribing team; do not stop a prescribed treatment solely because of a general risk estimate. See the semaglutide overview for the trial numbers and product context.51
Sources, kept close.
Selected supporting sources; this is not a complete literature review.
- Semaglutide (Wegovy, Ozempic and Rybelsus): risk of non-arteritic anterior ischaemic optic neuropathy (NAION)UK Medicines and Healthcare products Regulatory Agency · UK medicines safety update, 5 February 2026
- PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicinesEuropean Medicines Agency · EU regulator safety review, 2025
- New-onset NAION and initiators of semaglutide in US veterans with type 2 diabetesJAMA Ophthalmology · Observational cohort study, February 2026
- Diabetic retinopathyUS National Eye Institute · US public-health patient guide
- Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT)New England Journal of Medicine / PubMed · Randomized controlled trial