US FDA orders new safety warnings on weight-loss drugs over potential risk of vision loss

The US Food and Drug Administration (FDA) has informed patients and healthcare providers of a potential increased risk of a serious eye condition that may lead to sudden blindness associated with the use of GLP-1 drugs for weight loss and diabetes.

The FDA has said that GLP-1 drugmakers must add a warning label about the rare eye condition, called nonarteritic anterior ischaemic optic neuropathy, or NAION, which affects the optic nerve that carries signals from the eye to the brain.

The condition is a common cause of sudden, painless vision loss and may lead to permanent impairment of sight. It is caused by decreased blood flow to the front part of the optic nerve. When blood flow to the nerve is reduced or blocked, it can cause sudden vision loss. The condition is permanent with no known treatment.

The FDA said on Monday that “there is a potential increased risk of rare NAION” in people taking GLP-1 drugs.

The agency’s requirement applies to all GLP-1s, including Novo Nordisk’s Ozempic and Wegovy and Eli Lilly’s Mounjaro and Zepbound, as well as several older GLP-1 diabetes medications.

Previous research has found that GLP-1 use may increase the risk of NAION.

The FDA said it began looking into a possible link after a 2024 study published in JAMA Ophthalmology found diabetes patients prescribed semaglutide were four times as likely to develop NAION as those not prescribed the drug.

The agency said it reviewed reports of side effects submitted to its adverse event monitoring system and analysed data from multiple clinical trials. Cases of NAION have been reported for all currently marketed GLP-1 drugs, the FDA found. However, FDA scientists were not able to identify a mechanism for how the drugs could increase the risk of the eye condition.

Risk factors for NAION can overlap with conditions seen in people taking GLP-1 drugs, including Type 2 diabetes, obesity, sleep apnoea and hypertension.

“Patients and caregivers should be aware of a potential increased risk of NAION, a rare condition that can result in acute, painless, decreased vision in one eye, including permanent vision loss,” with GLP-1 use, the FDA said in the release.

Spokespersons for both Novo Nordisk and Eli Lilly said patient safety is their top priority.

The drug labels from Novo Nordisk and Lilly also carry other warnings, including for pancreatitis, gallbladder problems and kidney injury.

The labels also carry a black box warning — the FDA’s strongest safety warning — about a possible risk of thyroid tumours.

Last year, the ⁠European Medicines Agency’s safety committee said NAION may affect up to 1 in 10,000 people taking semaglutide for at least one year. That was the first ⁠time a regulator had confirmed the side effect.

Four patients in Denmark, who experienced vision loss after using GLP-1 drugs, were granted compensation, the Danish Patient Compensation had said.