FDA warns of vision loss risk linked to popular GLP-1 drugs like Wegovy, Zepbound

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The U.S. Food and Drug Administration is requiring new safety warnings on all GLP-1 drugs after finding evidence of a potential increased risk of a rare eye condition, the agency said on Monday.

The condition, which can cause sudden vision loss, known as nonarteritic anterior ischemic optic neuropathy (NAION), is rare, and a causal relationship has not been established.

The FDA is requiring the makers of all GLP-1 medications to add a warning about the potential increased risk of NAION associated with use of these medications, it said.

NAION is a condition that can result in sudden decreased vision, including permanent vision loss. It is caused by decreased blood flow to the front part of the ​optic nerve — the underlying cause is not completely understood, however.

NAION cases have been reported for all currently marketed GLP-1 products, the FDA said.

Ozempic and Wegovy maker Novo Nordisk said it "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."

Eli Lilly, the company behind Mounjaro, Zepbound and Foundayo, said it is "carefully evaluating the update and will respond to FDA promptly." Patient safety is Lilly's "top priority," the drugmaker added.

Diabetes itself is a known risk factor for NAION, complicating efforts to determine if cases among GLP-1 users are caused by the medications or by patients' underlying health conditions.

The FDA decision follows a review of clinical trials, real-world patient data, and published studies.

An analysis of 126 trials involving more than 134,000 patients found 6.4 cases of NAION per 100,000 patient-years among GLP-1 users, compared with 3.8 among patients receiving other treatments or placebos.

The FDA said it identified 15 probable NAION events, 10 in patients treated with GLP-1s and five in patients receiving a placebo, and no cases were identified among patients receiving other non-GLP-1 glucose-lowering medications.

Several observational studies also identified an increased risk, supporting the FDA's concerns.

The agency's findings were more mixed when comparing the risk of developing NAION from the use of GLP-1 drugs versus other commonly prescribed diabetes drugs.

Real-world patient data found a statistically significant increase in the risk of NAION among GLP-1 users compared with patients taking DPP-4 inhibitors, another class of diabetes medications, but not compared with those taking SGLT-2 inhibitors, per the FDA. SGLT-2 inhibitors are another class of medicines that includes Jardiance and Farxiga.

However, observational studies consistently reported an increased risk of NAION in patients with type 2 diabetes mellitus who started a GLP-1 treatment compared to those who initiated DPP-4 inhibitors or SGLT-2 inhibitors, the FDA added.

The FDA's class-wide labeling action is "likely to attract attention but should have limited impact on GLP-1 uptake," according to Citi analysts.

It 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 the medicines, they added.

Benefits versus risks

While GLP-1 drugs have been shown to lead to benefits beyond weight loss and controlling blood sugar levels, many also carry the FDA's strongest safety warning, known as a boxed warning, over a potential risk of thyroid tumors.

Studies have shown that semaglutide, the active ingredient in Wegovy and Ozempic, and tirzepatide, the active ingredient in Mounjaro, cause thyroid C-cell tumors in rodents. It remains unknown whether the drugs cause these tumors, including a rare form of thyroid cancer, in humans.

Both semaglutide and tirzepatide also carry warnings about diabetic retinopathy, another eye condition that can lead to blurred vision, difficulty seeing in low light, and, eventually, sight loss. Diabetic retinopathy is when high blood sugar damages the tiny blood vessels in the retina, the light-sensitive tissue at the back of the eye.

In a two-year trial involving patients with type 2 diabetes and high cardiovascular risk, diabetic retinopathy complications occurred in 3% of patients treated with Ozempic, compared with 1.8% of those receiving a placebo, according to the drug's prescribing information.

Mounjaro's FDA label separately warns that rapid improvements in blood sugar control have been associated with temporary worsening of diabetic retinopathy and recommends monitoring patients with a history of the condition.

FDA decision follows European warnings

European regulators flagged a risk of NAION associated with semaglutide in June 2025.

The European Medicines Agency's safety committee concluded that NAION was a very rare side effect of semaglutide that may affect up to 1 in 10,000 people taking it, and recommended updating the drug's product information. The U.K.'s medicines regulator followed with a similar warning in February.

Unlike the FDA's latest action, which covers all GLP-1 medications, the European and British warnings focused specifically on semaglutide.

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