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The FDA, the United States drug regulatory agency, has determined that manufacturers of weight-loss pens in the GLP-1 agonist class must include in their package inserts warnings about an increased risk of a serious eye condition associated with the use of the medications.
The manufacturers of Ozempic, Wegovy, Mounjaro and Zepbound must warn about the risks related to non-arteritic anterior ischemic optic neuropathy, also known by the acronym Naion.
This disease occurs when the blood vessels that supply the optic nerves become obstructed, depriving them of oxygen.
The condition can cause a painless decrease in vision in one eye, which can be permanent, according to the FDA.
In a statement to the BBC, the American Academy of Ophthalmology said that "any additional risks appear small, and these medications have not been proven to cause Naion."
"GLP-1 medicines offer important benefits for people with diabetes, obesity and heart disease, so our message to patients is simple," the group said. "Do not stop medication without consulting your doctor, and if you notice a sudden, painless loss of vision in one of your eyes, see an ophthalmologist immediately."
In Brazil, Anvisa (National Health Surveillance Agency) is investigating 13 reports of suspected blindness among people who use weight-loss pens.
In June 2025, the agency issued a warning about Naion as a very rare adverse event associated with semaglutide and determined the inclusion of this risk in the leaflets of medicines that contain the active ingredient.
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There is no known treatment to reverse vision loss caused by Naion. According to experts, this is the most common cause of acute optic nerve damage in people over 50 years of age.
The FDA said it conducted a detailed analysis of reports of Naion in GLP-1 users, as well as a review of other studies, and concluded that there is an "increased risk of rare events from Naion" in people taking these medications.
In a statement, Novo Nordisk, maker of Wegovy, one of the most popular weight-loss drugs, said it believes the data "does not establish a cause-and-effect relationship."
"We recognize that Naion can have a profound impact on patients and their families. Patient safety is a top priority for Novo, and we continue to monitor the safety of our medicines," the manufacturer said.
According to the US regulatory agency, some research has been difficult to analyze because people who take GLP-1 medications for obesity and type 2 diabetes may already have risk factors for Naion regardless of the medications.
The FDA said it is not known why those who take GLP-1 medications may be at greater risk of developing the eye disease.
The medications already have warnings on their labels for several other conditions, including pancreatitis and gallbladder disease.
Some of the most common symptoms associated with semaglutide — a key ingredient in many GLP-1 class medications — include nausea, vomiting, and stomach pain.
Last year, a safety body at the European Medicines Agency, which is part of the European Union, said that up to 1 in 10,000 people taking semaglutide could be affected by Naion.
In a study published two years ago that looked at 17,000 patients, American researchers found that those taking semaglutide were four times more likely to be diagnosed with Naion than those not taking the drug.
But one of the study's authors, Harvard Medical School Ophthalmology Professor Dr. Joseph Rizzo, said the findings were "significant but tentative" and that more research was needed into the relationship between the drug and eye condition in a more diverse population.
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