Federal health regulators announced Monday that drugmakers must add a new safety warning to popular GLP-1 medications, alerting patients to a rare eye condition that can trigger sudden and permanent vision loss.
The Food and Drug Administration said the updated warning applies to all drugs in the GLP-1 class, which includes blockbuster medications such as Novo Nordisk’s Ozempic and Wegovy, as well as Eli Lilly’s Mounjaro and Zepbound. The warning focuses on nonarteritic anterior ischemic optic neuropathy, or NAION, an incurable disorder caused by restricted blood flow to the optic nerve, which transmits visual signals between the eye and the brain.
Review of Clinical Trials and Adverse Events
The FDA initiated its review following a 2024 study in JAMA Ophthalmology that showed diabetes patients taking semaglutide were four times as likely to develop NAION compared to those on other treatments. The agency examined animal data, adverse event databases, and findings from more than 125 clinical trials, the Associated Press reported.
In those clinical trials, NAION occurred in approximately six of every 100,000 patients who took a GLP-1 drug for at least one year, according to the AP. By comparison, fewer than four out of 100,000 individuals taking a placebo or other glucose-lowering drugs developed the condition.
Although cases were documented across every GLP-1 product currently on the market, FDA scientists noted that they could not confirm a biological mechanism explaining how the medications might trigger the disorder. The agency also pointed out that risk factors for NAION often overlap with the health profiles of patients who use GLP-1 treatments, such as Type 2 diabetes, obesity, hypertension and sleep apnea.
Drugmakers and Doctors Respond
Spokespeople for both Novo Nordisk and Eli Lilly emphasized that patient safety remains their top priority. Novo Nordisk stated that available data do not prove a direct cause-and-effect connection, adding that the company stays confident in the overall safety and benefit profile of its therapies, CNN reported. Eli Lilly said it is evaluating the FDA communication and intends to submit a prompt response.
Medical specialists stressed that while the warning is warranted to raise awareness, the risk remains exceptionally low. According to the American Academy of Ophthalmology, NAION is the second most common optic nerve disease in the U.S., affecting up to 10 out of 100,000 adults over age 50.
Dr. Manjot Gill, an ophthalmologist at Northwestern Medicine in Chicago, told NBC News that patients should not panic or abruptly quit their prescriptions. Gill noted that the warning primarily serves to ensure patients consult an eye specialist promptly if they notice any changes in sight.
Symptoms and Medical Advice
The FDA instructed doctors to educate patients about potential warning signs and to consider stopping GLP-1 therapy if NAION develops, unless the clinical benefits clearly outweigh the risks. The agency noted that symptoms frequently appear upon waking and can include:
- Acute, painless loss of sight in one eye
- Hazy or blurred vision
- Missing patches of sight or visual field blind spots
- Distorted perception of colors
GLP-1 treatments already feature warnings for health issues including pancreatitis, kidney injury, gallbladder disease and a boxed warning regarding thyroid tumors. What remains unknown is whether ongoing global studies will uncover a definitive causal mechanism, or whether international regulatory bodies will mandate further prescription limits as use continues to surge.
