“Semaglutide causes blindness (NAION).”
What the evidence shows
A 2024 study in JAMA Ophthalmology (Hathaway et al.) found semaglutide-treated patients had higher rates of non-arteritic anterior ischemic optic neuropathy (NAION) — a rare, sudden, usually painless loss of vision in one eye, sometimes called an "eye stroke." A larger independent 2025 follow-up across 14 databases and millions of patients (Cai et al.) found an elevated but modest association in some analyses and inconsistent results in others, with no established mechanism. Both teams frame it as an observational signal, not proven cause. Regulators have split: as of mid-2026 the EU (EMA) and UK (MHRA) have added NAION to semaglutide product information as a labeled "very rare" (up to 1 in 10,000) effect on a precautionary basis, and the WHO flagged it as a potential risk — while the US FDA labels carry no NAION entry.
What we still don’t know
Whether semaglutide actually causes NAION — versus the association reflecting confounding, since diabetes and cardiovascular disease independently raise NAION risk — is unresolved. There's no proven biological mechanism, and because NAION is rare to begin with, even a real relative increase would translate to a very small absolute number of extra cases. Larger prospective studies are needed.
Why the claim misleads
"Causes blindness" makes a rare, single-eye, still-unproven association sound like a common, guaranteed, total-vision catastrophe. Even the regulators who acted did so precautionarily — the EMA cites roughly a two-fold association, and the MHRA notes a report "does not mean it was definitely linked." It's a signal worth monitoring (sudden vision change in one eye warrants urgent eye care), not a demonstrated cause-and-effect.
Graded by The Peptide Era · evidence, not hype