Semaglutide and NAION: What the Evidence Says
Last updated: October 2026
Semaglutide (Ozempic, Wegovy, Rybelsus) is now one of the most prescribed drugs in the world. In 2024 a single-centre study linked it to non-arteritic anterior ischaemic optic neuropathy (NAION), and in 2025 the European Medicines Agency concluded that NAION is a very rare side effect. Expect patients and physicians to ask you about it.
NAION in one paragraph
Typically a patient over 50 wakes with painless loss of vision in one eye, an altitudinal (often inferior) field defect, an RAPD and a swollen, often sectoral, hyperaemic disc. The fellow eye usually has a small, crowded disc with little or no cup (the "disc at risk"). Risk factors include diabetes, hypertension, obstructive sleep apnoea, nocturnal hypotension, and drugs such as PDE5 inhibitors and amiodarone. Always exclude giant cell arteritis first (ESR, CRP, platelets, and the symptom history). See optic neuritis vs NAION vs arteritic AION.
How the signal emerged
| Evidence | Finding | Caveats |
|---|---|---|
| Hathaway et al., JAMA Ophthalmology 2024 (single US neuro-ophthalmology centre, matched cohort, n=1,689) | Hazard ratio for NAION: 4.28 in type 2 diabetes and 7.64 in overweight or obesity. 36-month cumulative incidence: 8.9% vs 1.8% in the type 2 diabetes cohort. | Retrospective. Drawn from a referral population already enriched for optic nerve disease. Small event numbers. |
| Later large database and registry studies | Mixed results: several found a smaller increase in risk, about a doubling, and some found none. | Observational, and coding of NAION in databases is imperfect. |
| EMA PRAC review, June 2025 | NAION is a very rare side effect of semaglutide (up to 1 in 10,000 users). Risk is about twice that of non-users with type 2 diabetes, roughly one extra case per 10,000 person-years. Product information was updated. | The conclusion applies to semaglutide. Data on other GLP-1 agonists and on tirzepatide are limited. |
Putting the risk in proportion
- NAION is uncommon, with an incidence of roughly 2–10 per 100,000 a year in people over 50. Doubling a rare risk still leaves a rare event.
- The people who take semaglutide (those with diabetes, obesity or sleep apnoea) already carry a higher baseline risk of NAION, which makes confounding hard to remove.
- Proposed mechanisms include rapid metabolic and blood-pressure changes at the optic nerve head and possible GLP-1 receptor effects. None is proven.
What to do in clinic
| Situation | Suggested approach |
|---|---|
| Patient asks whether to start semaglutide | Explain that the risk is very rare and that the metabolic benefits are large. Ask about previous NAION in either eye, and note a crowded disc or untreated sleep apnoea. The decision belongs to the patient and their physician. |
| Previous NAION in one eye | Discuss the fellow-eye risk with the prescriber; it is about 15% over 5 years even without semaglutide (IONDT). Many neuro-ophthalmologists would advise caution or an alternative drug. |
| Sudden painless vision loss on semaglutide | Same-day assessment. Rule out GCA, document the disc and fields, and arrange OCT of the RNFL. |
| NAION confirmed on semaglutide | The EMA advises stopping semaglutide; arrange this with the prescriber. Manage vascular risk factors and screen for sleep apnoea. There is no proven treatment for NAION itself: optic nerve sheath decompression was not beneficial in IONDT, and steroid benefit is unproven. |
Viva pearls
- NAION has a "disc at risk" (small cup-to-disc ratio). Arteritic AION often has chalky white pallid swelling and a normal-sized cup.
- EMA frequency categories: very rare means fewer than 1 in 10,000.
- Other drugs associated with NAION include PDE5 inhibitors (sildenafil) and amiodarone (whose optic neuropathy is often bilateral and slowly progressive).
- Observational association is not causation. Know the difference between a signal, a confirmed adverse reaction and a class effect.
Related: giant cell arteritis, optic disc oedema flowchart and systemic drugs and diabetic retinopathy.
Key sources
- EMA: PRAC concludes NAION is a very rare side effect of semaglutide (June 2025)
- The Pharmaceutical Journal: EMA review report
- Hathaway et al. 2024 summary (Ophthalmology Times)
- Ischemic Optic Neuropathy Decompression Trial Research Group. JAMA 1995;273:625–32
📘 Want more exam-ready material? See Most Commons in Ophthalmology on Kindle, or browse all my books.
Looking for an eye specialist in Ahmedabad? Read about neuro-ophthalmology care at Sadbhaav or book a consultation with Dr. Dhaval Patel.
