Sudden, painless vision loss: FDA adds rare eye condition warning to popular GLP-1 drugs

The US Food and Drug Administration (FDA) has flagged a potential increased risk of a rare eye condition that can cause permanent vision loss among users of popular GLP-1 drugs, including Ozempic, Wegovy, Mounjaro and Zepbound. The regulator has asked manufacturers to add warnings about the condition to the labels of all medicines in the drug class.

In a safety communication issued on Monday, the FDA said the warnings and precautions section of GLP-1 drug labels must include information about the potential risk of non-arteritic anterior ischemic optic neuropathy (NAION).

The condition, which is caused by reduced blood flow to the optic nerve, is a common cause of sudden, painless vision loss and can result in permanent impairment of sight. Its underlying cause, however, is not fully understood.

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The FDA's action follows an investigation that began after a 2024 medical paper linked NAION to certain patients taking semaglutide, the active ingredient in Novo Nordisk's Ozempic and Wegovy.

An FDA analysis of more than 125 clinical trials found that NAION occurred in approximately six out of every 100,000 patients who took a GLP-1 drug for at least a year. The comparable rate among people taking a placebo or other glucose-lowering medications was fewer than four per 100,000.

The regulator said it had also examined animal data and post-marketing evidence, including observational studies and reports of adverse events.

Symptoms include blurred vision, blind spots, distorted colours and other visual disturbances. Patients experiencing these symptoms have been advised to contact a healthcare professional immediately.

The warning applies to all medicines with GLP-1 receptor agonist activity, including injectable and oral treatments used for obesity, diabetes and other medical conditions.

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Drugmakers maintained that the available evidence did not establish a direct causal relationship. A Novo Nordisk spokesperson said the company remained confident in the benefit-risk profile of its GLP-1 medicines, while Eli Lilly said it was evaluating the FDA's update.

The warning follows a similar move by the European Medicines Agency's safety committee last year, which said NAION could affect up to one in 10,000 people taking semaglutide for at least a year.

A large study published in 2025, tracking nearly 175,000 diabetic patients taking semaglutide and an equal number on other medications, found that the risk of NAION more than doubled after two years of treatment compared with other diabetes drugs.

(With agency inputs)