The Food and Drug Administration (FDA) announced Monday that manufacturers of GLP-1 drugs must include a warning label about a rare eye condition that can cause sudden blindness.
The condition, known as non-arteritic anterior ischemic optic neuropathy (NAION), affects the optic nerve, which transmits signals from the eye to the brain. When blood flow to the nerve is reduced or blocked, it can cause sudden vision loss.
The condition is permanent and there is no known treatment.
The FDA noted that “there is a possible increased risk of NAION, a rare condition” in people who use GLP-1 drugs.
The agency’s requirement applies to all GLP-1 drugs, including Novo Nordisk’s Ozempic and Wegovy, and drugmaker Eli Lilly’s Mounjaro and Zepbound, as well as several older diabetes drugs that contain the substance.
Spokespeople for both Novo Nordisk and Eli Lilly said patient safety is their top priority.
Previous research has revealed that GLP-1 use could increase the risk of NAION, and Lilly has stated that it was aware of studies on this possible relationship.
The FDA said it began investigating a possible link following a 2024 study published in JAMA Ophthalmology, which found that patients with diabetes who were prescribed semaglutide were four times more likely to develop NAION than those who were not prescribed the drug.
The agency said it reviewed side effect reports submitted to its adverse event monitoring system and analyzed data from multiple clinical trials. The FDA found that cases of NAION have been reported with all GLP-1 medications currently on the market. However, agency scientists were unable to identify a mechanism to explain how these medications might increase the risk of this eye condition.
NAION risk factors may overlap with conditions seen in people taking GLP-1 medications, including type 2 diabetes, sleep apnea, and hypertension.
NAION is the second most common optic nerve disease in the United States, affecting up to 10 in every 100,000 people over age 50, according to the American Academy of Ophthalmology.
“Patients and their caregivers should be aware of a possible increased risk of NAION, a rare condition that can cause an acute, painless decrease in vision in one eye, including permanent vision loss,” with the use of GLP-1, the FDA said in the statement.
Novo Nordisk and Lilly’s drug labels also include other warnings, including about pancreatitis, gallbladder problems and kidney damage.
They also have a “black box” warning—the FDA’s most serious safety warning—about a possible risk of thyroid tumors.
