The US Food and Drug Administration is requiring new warning information for a group of popular GLP-1 drugs used for weight loss and diabetes. The agency alerted patients and healthcare providers on Monday to a potential increased risk of a serious eye condition associated with their use.

The labeling change covers Eli Lilly’s Mounjaro and Zepbound, as well as Novo Nordisk’s Ozempic and Wegovy. The FDA said information about the potential increased risk must be added to the “warnings and precautions” section of the drugs’ labeling.

The condition is non-arteritic anterior ischemic optic neuropathy, also known as NAION. It is a common cause of sudden and painless vision loss, and in some cases it may result in permanent impairment of sight.

NAION occurs when blood flow to the front portion of the optic nerve decreases. The underlying cause of that reduction in blood flow is not completely understood, according to the information provided.

The FDA said it evaluated several types of evidence before taking action. Its review included clinical trial data, animal data and postmarketing information, including observational studies and case reports.

Eli Lilly said the communication was not focused on findings involving its products specifically. A company spokesperson said Lilly was evaluating the FDA update and planned to respond promptly.

“FDA’s drug safety communication applies to all medicines with GLP-1 RA activity and does not reference any findings specific to Lilly medicines. We are carefully evaluating the update and will respond to FDA promptly,” said a Lilly spokesperson.

Novo Nordisk also responded to the FDA action while defending the overall profile of its medicines. The company maintained that the available information does not establish that its GLP-1 products cause the condition.

“Novo 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,” a spokesperson for Novo said.

Citi analyst Geoff Meacham said the FDA action could temporarily heighten concern among patients and investors. However, he said the rarity of NAION and the drugs’ reported benefits should limit changes in prescribing.

“The FDA action may temporarily increase patient and investor concern, but the rarity of NAION and substantial weight, glycemic, cardiovascular, renal, and sleep apnea benefits should preserve a favorable benefit-risk profile and limit changes to prescribing,” Meacham said.

The FDA decision follows action taken last year by the European Medicines Agency’s safety committee. That committee said NAION may affect up to 1 in 10,000 people who take semaglutide for at least one year.

Semaglutide is the active ingredient in Novo Nordisk’s Wegovy and Ozempic, as well as its diabetes drug Rybelsus. The European finding marked the first time a regulator had confirmed the side effect.

Separate cases also emerged in Denmark. Danish Patient Compensation said last year that four patients who experienced vision loss after using Novo Nordisk’s GLP-1 drugs had been granted compensation.

A large study published in 2025 examined the issue among people with diabetes. Researchers tracked nearly 175,000 patients treated with semaglutide and an equal number who were taking non-GLP-1 medications.

The study found that the risk of NAION more than doubled after two years of treatment with a GLP-1 drug when compared with diabetes medicines from other classes. The finding added to the evidence regulators have considered while examining the potential eye risk.

For now, the FDA action centers on adding the potential risk to drug labeling and informing patients and healthcare providers. Lilly is evaluating the update, while Novo Nordisk continues to dispute that the data establish a causal relationship.