A new study published in Neurology and covered by Women's Health reports a link between semaglutide use and a higher risk of a rare condition that can cause permanent vision loss. Researchers pooled data from nearly 1.6 million patients across five studies, of whom 682,456 used semaglutide and 911,098 used other medications.

The condition is non-arteritic anterior ischemic optic neuropathy, or NAION, and semaglutide is the peptide sold as Ozempic and Wegovy. NAION is thought to result from reduced blood flow to the optic nerve head, per Brigham and Women's Hospital, and the American Academy of Ophthalmology says it can come on suddenly, cause permanent vision loss, and has no effective treatment.

The percentage and the denominator

The headline figure is a 152 percent higher risk of NAION among semaglutide users compared with people on other drugs, and 141 percent higher among patients with diabetes. That is the kind of number that travels well and explains almost nothing on its own.

The absolute rate is where the story sits: 118 cases of NAION per 100,000 semaglutide users overall, and 125 per 100,000 among people with type 2 diabetes. Both work out to a fraction of a percent, which is the sort of context that usually goes missing by the third repost.

Not the first flag

This is not a new signal. Research published in JAMA Ophthalmology in 2024 found overall NAION cases in GLP-1 users were low, but that people with diabetes taking semaglutide were more than four times as likely to be diagnosed, rising to seven times among people with overweight or obesity.

The confounding problem

The study's authors wrote that the findings "warrant further investigation and should inform clinical risk-benefit discussions," which is a long way from a causal claim. Ophthalmologist Bavand Youssefzadeh told Women's Health that most patients who develop NAION already have risk factors such as diabetes, high blood pressure, sleep apnea, or a crowded optic nerve.

That overlap is the whole difficulty, since the people most likely to be prescribed these drugs are already the people most likely to get NAION. Youssefzadeh said one possibility is that dehydration, lower blood pressure, or rapid blood sugar changes could temporarily affect circulation to the optic nerve, but that direct causation is not established.

Bottom line

Mir Ali, medical director of MemorialCare Surgical Weight Loss Center, called it "a very, very low-risk complication" and noted that nobody has recommended stopping the medications for patients with diabetes or high blood pressure. What remains unsettled is whether the drug contributes to NAION at all, or whether the patients taking it were always the ones at risk.