FDA warns of rare vision-loss side effect from GLP-1 drugs

Popular weight loss and diabetes drugs, including Ozempic and Wegovy, will carry a new warning about a possible rare side effect that can sometimes lead to permanent vision loss, U.S. health regulators announced Monday.

The Food and Drug Administration said the risk will be added to the labeling of all GLP-1 drugs, the blockbuster medications used to treat obesity, diabetes and several other medical conditions. The class includes a dozen injectable or pill-based drugs, including widely used brands like Zepbound and Mounjaro.

The eye condition, known as non-arteritic anterior ischemic optic neuropathy, or NAION, can cause significant vision loss. The problem, which has been reported with all GLP-1 drugs, is caused by decreased blood flow to the optic nerve, although the underlying cause isn't understood, the FDA said.

FDA scientists began looking into the problem after the publication of a 2024 medical paper tying the condition to certain patients taking semaglutide, the active drug in Novo Nordisk's Ozempic and Wegovy.

Dr. Joseph Rizzo, a neuro-ophthalmologist who co-authored that paper, told CBS News on Monday that he and his team had been working with the FDA to gather and review data on the issue for some time and that, while he didn't know the agency was ready to make a decision, he wasn't surprised it chose to add the warning. 

He stressed that while he believes the evidence shows GLP-1 usage increases the risk of developing NAION, he doesn't discourage patients from taking them, saying, "The medicines have really been profoundly beneficial to a large number of people."

People who aren't on GLP-1s can also develop NAION, which affects somewhere between 2 to 10 of every 100,000 adults over age 50, according to the American Academy of Ophthalmology.

Novo Nordisk, the maker of Wegovy and Ozempic, said it "continues to believe the data do not establish a cause-and-effect relationship and we remain confident in the benefit-risk profile of our GLP-1 medicines."

"We recognize that NAION can have a profound impact on patients and their families," it said. "Patient safety is a top priority for Novo, and we continue to monitor the safety of our medicines, review new research and work with health authorities around the world."

Eli Lilly, which makes Zepbound and Mounjaro, said in a statement Monday it was "carefully evaluating the update and will respond to FDA promptly."

"Patient safety is Lilly's top priority," the company said. "FDA's drug safety communication applies to all medicines with GLP-1 RA activity and does not reference any findings specific to Lilly medicines."

An FDA analysis of more than 125 clinical trials found that the problem occurred in roughly 6 of every 100,000 patients who took a GLP-1 for at least one year. The comparable rate for people taking a placebo or other types of glucose-lowering medications was less than 4 per 100,000, the FDA said.

The agency also found reports of the problem in its electronic reporting system for drug injuries and side effects.

Symptoms of the problem include blurred vision, blind spots, distorted colors and other visual disturbances, according to the FDA. Patients experiencing such problems should contact a health care professional immediately, the agency said.

Rizzo noted that the vision loss from the condition tends to be irreversible and can become progressively worse, even if a patient stops taking the medication.

"Usually when you lose vision, although there may be some mild degree of improvement, it's usually not a large degree of improvement," he said. "And unfortunately, a great frustration for so many of our patients and doctors who take care of patients with NAION is the fact that we do not really know how to mitigate the risk."

Rizzo also said the condition does not necessarily affect each eye the same.

"The degree of visual loss in the first eye does not inform the degree of visual loss that would occur in the second eye," he told CBS News. "So you could have mild visual loss in one eye, and then the next eye could be severe."