The U.S. Food and Drug Administration is requiring new safety warnings for all GLP-1 drugs after finding evidence of a potential increased risk of rare eye diseases, the agency announced Monday.
Known as non-arteritic anterior ischemic optic neuropathy (NAION), this condition that can cause sudden loss of vision is rare and no causal relationship has been established.
The FDA said it is asking manufacturers of all GLP-1 drugs to add warnings about the possible increased risk of NAION with the use of these drugs.
NAION is a condition that can cause sudden vision loss, including permanent vision loss. This is caused by decreased blood flow to the anterior part of the optic nerve, but the underlying cause is not fully understood.
According to the FDA, cases of NAION have been reported with all GLP-1 products currently on the market.
Ozempic and Wegovy Manufacturers novo nordisk The company said it “continues to believe that the data do not establish a causal relationship and remains 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 promptly to the FDA.” Patient safety is Lilly’s “top priority,” the drugmaker added.
Diabetes itself is a known risk factor for NAION, complicating efforts to determine whether cases among GLP-1 users are caused by the drug or by the patient’s underlying health condition.
The FDA’s decision followed a review of clinical trials, real-world patient data, and published research.
An analysis of 126 trials involving more than 134,000 patients found 6.4 cases of NAION per 100,000 patient-years in GLP-1 users, compared with 3.8 cases in patients receiving other treatments or a placebo.
The FDA said it identified 15 probable NAION events, 10 of which occurred in patients treated with GLP-1, five in patients who received a placebo, and no cases were identified in patients receiving other non-GLP-1 hypoglycemic agents.
Several observational studies have also confirmed an increased risk, supporting FDA’s concerns.
The agency’s findings were more mixed when comparing the risk of developing NAION with the use of GLP-1 drugs and the use of other commonly prescribed diabetes drugs.
According to the FDA, real-world patient data found a statistically significant increased risk of NAION in GLP-1 users compared to patients taking DPP-4 inhibitors, another class of diabetes drugs, but not compared to patients taking SGLT-2 inhibitors. SGLT-2 inhibitors are another class of medications, such as Jardiance and Farxiga.
However, the FDA added that observational studies have consistently reported an increased risk of NAION in patients with type 2 diabetes starting GLP-1 therapy compared to patients starting DPP-4 inhibitors or SGLT-2 inhibitors.
Citi analysts said the FDA’s class-wide labeling action “is likely to garner attention, but would have limited impact on GLP-1 uptake.”
They added that while patient and investor concerns may be temporarily heightened, NAION’s rarity and substantial effects on weight, blood sugar, cardiovascular, renal, and sleep apnea should maintain a favorable efficacy-risk profile and limit re-formulation of the drug.
Benefits and risks
GLP-1 drugs have been shown to do more than just weight loss and control blood sugar levels, but many also carry the FDA’s strongest safety warnings (known as boxed warnings) regarding the potential risk of thyroid tumors.
Studies have shown that semaglutide, the active ingredient in Wigovy and Ozempic, and tirzepatide, the active ingredient in Mounjaro, cause thyroid C-cell tumors in rodents. It remains unclear whether these drugs cause these tumors, including rare forms of thyroid cancer, in humans.
Both semaglutide and tirzepatide also carry warnings about diabetic retinopathy, another eye disease that can lead to blurred vision, difficulty seeing in low light, and ultimately vision loss. Diabetic retinopathy is when high blood sugar levels damage the small blood vessels in the retina, the light-sensitive tissue at the back of the eye.
According to the drug’s prescribing information, in a two-year study in patients with type 2 diabetes who are at high cardiovascular risk, diabetic retinopathy complications occurred in 3% of patients treated with Ozempic, compared with 1.8% of patients given a placebo.
Munjaro’s FDA label separately warns that rapid improvement in glycemic control is associated with temporary worsening of diabetic retinopathy and recommends monitoring in patients with a history of diabetic retinopathy.
FDA decision follows European warning
European regulators warned of NAION risks associated with semaglutide in June 2025.
The European Medicines Agency’s safety committee concluded that NAION is an extremely rare side effect of semaglutide, potentially affecting 1 in 10,000 users, and recommended that the drug’s product information be updated. Britain’s medicines regulator issued a similar warning in February.
Unlike the FDA’s latest action, which covers all GLP-1 drugs, the European and UK warnings focused specifically on semaglutide.
