What GLP-1 users should know about the potential risk of a rare type of vision loss

Dozens of Americans have filed personal injury lawsuits against the makers of popular GLP-1 drugs, like Ozempic, Wegovy and Mounjaro, claiming they were not properly warned of the risk of a rare type of sudden vision loss, called nonarteritic anterior ischemic optic neuropathy, or NAION, when taking the medications.

Researchers have been studying a possible link between GLP-1 drugs and this eye condition in recent years after a possible safety signal was reported from a single health center in Boston in 2024, but so far, no study has proven these drugs are the cause.

Novo Nordisk, the maker of Ozempic and Wegovy, said they take “all reports of adverse events very seriously,” and pushed back against these claims, stating, “Novo believes the personal injury lawsuits filed in the U.S. are without merit and are vigorously defending them,” a spokesperson told ABC News.

Adding, "Novo is committed to patient safety and continuously monitors the safety profile of our GLP-1 RA products. Should emerging safety data warrant further action, appropriate measures will be implemented in accordance with regulatory requirements.”

A spokesperson for Lilly, who manufactures Zepbound and Mounjaro, told ABC News, “Patient safety is Lilly’s top priority. We actively monitor, evaluate, and report safety information for all our medicines to the FDA. As part of our routine safety review process, we have ongoing discussions with regulators regarding potential safety topics, and we will continue to review data, including any data regarding ophthalmic issues."

Here’s what GLP-1 users should know about this condition and what the science says.

What is NAION?

Although a rare condition overall, Dr. John Chen, a professor of ophthalmology and neurology at Mayo Clinic, said, "NAION is the most common acute optic neuropathy in patients over the age of 50. It's essentially a lack of blood flow to the optic nerve, where patients typically have pretty acute onset of painless vision loss.”

That vision loss is usually permanent, and there is no specific treatment for the condition at this time, Chen told ABC News.

Dr. Raj Maturi, clinical spokesperson for the American Academy of Ophthalmology and ophthalmologist at Midwest Eye Institute, told ABC News that people with diabetes, regardless of GLP-1 use, can be at increased risk of developing this condition, and other risks include overnight low blood pressure or a very small optic nerve cup.

Vision problems are listed as possible side effects of these medications, but the Food and Drug Administration does not currently require the drug makers to list NAION as a specific risk.

The agency’s Sentinel Initiative does say a review is ongoing that aims to scientifically evaluate the possible safety signal related to GLP-1 drugs and NAION that is still in progress.

In a statement provided to ABC News, a spokesperson for the FDA said, "The FDA routinely monitors the safety of drug products postmarketing. The FDA identifies safety signals from a variety of sources, evaluates the available data and takes regulatory actions when appropriate.”

Other countries have required the drug makers to include a warning that there may be a possible increased risk of developing NAION if taking some of these medications based on their review of available evidence, including the European Medicines Agency and Australia’s Therapeutic Goods Administration, both citing it as a rare possible side effect.

In general, safety signals don’t always pan out as true risks for all medications and not every possible side effect is caused directly by the medication itself.

Drugs that are FDA-approved undergo rigorous clinical trials, are heavily scrutinized before reaching the market, and post-marketing safety is continuously monitored.

What does the science say? 

“Several studies suggest that there is a potential link between NAION, or eye stroke, and GLP-1 use,” Maturi said. “However it is important to note that causation has not been proven. And the risk does seem to be rare,” Maturi said.

In 2024, researchers at a single health system in Boston published data that suggested people with type 2 diabetes who were prescribed semaglutide, a GLP-1 receptor agonist and the active ingredient in Ozempic and Wegovy, may be at increased risk of developing this type of vision loss.

Since then, more research has been done with larger studies that have shown mixed results as to whether a link does exist, and no study to date has proven that these medications cause this eye condition.

"There are significant benefits from the GLP-1’s for severe obesity, diabetes, cardiovascular disease. That's proven time and time again with these randomized clinical trials,” Chen said. “We didn't have to pull the plug on those trials because people were going blind. So again, if there is an association, it's a very low risk."

The European Medicines Agency estimates this eye condition could possibly impact 1 out of every 10,000 GLP-1 users who have diabetes, based on their analysis of available information.

In a joint statement, the North American Neuro-Ophthalmology Society and the American Academy of Ophthalmology said, "While many report a small possible increased risk of NAION in patients taking GLP-1 RAs such as semaglutide, some studies report no correlation, and the overall magnitude of the risk of NAION remains low.”

Maturi and Chen both said that the data isn’t conclusive so far and more research is needed to understand if GLP-1 drugs have a true role in developing NAION.

What should GLP-1 users do? 

Doctors recommend that people always discuss any potential side effects of a medication with their own doctor and warn that there are proven health risks, including eye problems, if diabetes and obesity go untreated.

"For any patients already taking semaglutide who have not experienced any symptoms, they should continue to do so as instructed and discuss any questions or concerns with their primary care physician,” Maturi said.

Chen said he doesn’t believe this potential risk should prevent most people from using GLP-1 medications if they are recommended by a doctor to help treat an underlying health condition but cautions that people who have experienced NAION in one eye already may need to weigh the possible risks more closely with their doctor.

"We're not sure if the GLP-1 is connected or not. We know this helps with diabetes, heart disease, and severe obesity,” Chen said. "We essentially don't want you to stop your meds without talking to your doctor, and if you do have sudden painless vision loss, you should be seen by an eye doctor.”

Jade A. Cobern, MD, MPH, is a practicing physician, board-certified in pediatrics and general preventive medicine, and is a fellow of the ABC News Medical Unit. ABC News’ Elizabeth Schulze also contributed to this reporting.