FDA Orders Rare Vision Loss Warnings for GLP-1 Drugs as Taiwan Expands Safety Review

Warning expands beyond semaglutide to the whole drug class

The U.S. Food and Drug Administration is requiring all GLP-1 receptor agonist medicines to carry warnings about a rare eye condition that can cause sudden, painless and sometimes permanent vision loss. Its review of 126 clinical trials found 15 probable cases, including 10 among patients receiving GLP-1 drugs and five among those receiving a placebo.

The FDA announced the requirement in its November 9, 2026, drug safety communication. Manufacturers must add the potential risk of nonarteritic anterior ischemic optic neuropathy, known as NAION, to the Warnings and Precautions section of prescribing information.

Taiwan's Food and Drug Administration, or TFDA, says it will reassess the safety of the entire drug class. Taiwan previously focused its NAION communications and labeling instructions on semaglutide, the ingredient in Ozempic, Wegovy and Rybelsus. The broader U.S. action extends attention to other medicines with GLP-1 receptor activity, including tirzepatide products Mounjaro and Zepbound.

Which medicines and patients are affected?

GLP-1 medicines copy the action of a hormone released by the intestine after eating. They help lower blood sugar and act on areas of the brain that control appetite. Doctors prescribe them for type 2 diabetes and, depending on the product, weight management and other conditions.

The FDA's list covers injections and tablets, older medicines such as exenatide and liraglutide, and newer products such as orforglipron, sold as Foundayo and approved in 2026. Tirzepatide acts on both GLP-1 and another hormone receptor called GIP, so Mounjaro and Zepbound are also covered.

The requirement means patients and prescribers must receive clearer information about a potentially serious eye problem across the class. Decisions about continued treatment depend on the patient's condition, symptoms and expected benefits from the particular medicine.

What happens to the eye in NAION?

NAION develops when blood flow falls to the front of the optic nerve, the bundle of fibers that carries visual signals from the eye to the brain. Damage to this connection can leave parts of a person's vision blurred, missing or permanently lost.

The FDA says symptoms may appear suddenly in one eye, sometimes when a person wakes up. Warning signs include blind spots, tunnel vision, distorted colors and reduced sharpness in the center of sight. Because the condition can be painless, the absence of pain should not delay medical attention.

Smoking, diabetes, high blood pressure, sleep apnea, anemia and kidney disease are among the possible risk factors listed by the FDA. Several of these conditions are common among people prescribed GLP-1 medicines. A person who has experienced NAION in one eye also faces an increased risk in the other eye.

The biological explanation for a possible increase associated with GLP-1 treatment remains uncertain. The FDA's review of animal research identified no mechanism linking the medicines to the optic nerve injury.

How large was the risk in clinical trials?

The FDA combined 126 randomized controlled trials involving 134,253 patients because individual trials recorded few or no NAION cases. Of those patients, 78,217 received GLP-1 medicines and 56,036 received a placebo or another medicine for lowering blood sugar.

Across the trials, researchers identified 10 probable NAION events among GLP-1 users, five among placebo recipients and none among patients receiving other diabetes medicines. After accounting for the time participants were followed, the rates were 6.4 cases per 100,000 person-years for GLP-1 treatment and 3.8 for the comparison treatments.

A person-year measures time under observation: 100,000 people followed for one year contribute 100,000 person-years, as do 50,000 people followed for two years. The difference between the trial rates was 2.6 additional cases per 100,000 person-years, showing why the FDA describes the event as rare while warning that its consequences can be serious.

Health records showed different results by comparison drug

The FDA also examined adults with type 2 diabetes who started treatment between 2019 and 2024 through its Sentinel health data network. It compared GLP-1 medicines with two other groups of diabetes drugs, SGLT-2 inhibitors and DPP-4 inhibitors.

NAION rates were about 30 to 32 cases per 100,000 person-years among GLP-1 users, 31 among SGLT-2 inhibitor users and 26 among DPP-4 inhibitor users. These rates came from a different patient population than the clinical trials.

After statistical adjustment, the comparison with SGLT-2 inhibitors produced a hazard ratio of 1.19, with a 95% confidence interval of 0.91 to 1.54. The comparison with DPP-4 inhibitors produced a hazard ratio of 1.43, with an interval of 1.02 to 2.01. A hazard ratio compares how quickly events occur between groups; a value of one means equal risk.

The first comparison was not statistically significant because its uncertainty range included one. The second indicated a higher risk among GLP-1 users. The FDA considered these findings alongside clinical trials, published observational research, case reports and safety reports submitted after the drugs entered the market.

Another study following nearly 350,000 diabetes patients, roughly half taking semaglutide and half taking other diabetes medicines, found more than twice the NAION risk after two years among semaglutide users. The different populations and comparison treatments help explain why the size of the association varies between studies.

Taiwan's response builds on action taken in 2025

Taiwan's earlier semaglutide warning followed a June 6, 2025, assessment by the European Medicines Agency's Pharmacovigilance Risk Assessment Committee, known as PRAC. A semaglutide safety notice published by the Taiwan Drug Relief Foundation on July 1 reproduced the TFDA's June risk communication.

That notice described NAION as a very rare semaglutide side effect, with a stated frequency below one in 10,000. It also summarized large epidemiological studies suggesting roughly twice the risk among adults with type 2 diabetes taking semaglutide, equivalent to approximately one additional case per 10,000 person-years of treatment.

At the time, Taiwan had 14 approved semaglutide product licenses, covering different products, doses and presentations. Their Chinese prescribing information included diabetic retinopathy information, while NAION information was still awaiting regulatory action.

The main steps in the safety review have unfolded over more than two years:

• July 2024: Publication of a semaglutide study prompted the FDA to undertake further assessment.
• June 6, 2025: The European safety committee concluded that NAION should be listed as a very rare semaglutide side effect.
• June 2025: Taiwan issued a semaglutide risk communication.
• June 2026: Taiwan instructed semaglutide license holders to add NAION information to warnings and adverse reaction sections.
• November 9, 2026: The FDA announced warnings covering all GLP-1 receptor agonist medicines.

The TFDA now plans a safety reassessment covering the broader class and will decide on further risk controls after that review. It has not announced a completion date.

What Taiwan's 63 safety reports contain

Taiwan's national adverse drug reaction reporting system received 63 suspected reports involving GLP-1 medicines in 2026, according to Liu Chia-ping, a senior technical specialist in the TFDA's pharmaceutical division. Of these, 39 involved weight management and 24 involved diabetes treatment.

Weight management accounted for about 62% of those reports, calculated from 39 out of 63. Gastrointestinal problems were the most commonly described symptoms. Reported conditions included abdominal pain, intestinal obstruction and pancreatitis, alongside low blood sugar, nausea, vomiting and discomfort at injection sites.

The TFDA presented the total as suspected adverse reactions across several conditions. It did not specify a NAION count within those 63 reports or provide the number of patients using the medicines, which would be needed to calculate a local incidence rate.

Liu said manufacturers have been asked to submit plans for postauthorization safety studies, known as PASS, and risk management plans, known as RMP. These are tools for studying safety after approval and setting out how identified risks will be monitored and managed. Drug companies and medical institutions have also been asked to strengthen monitoring and reporting.

What patients should do about visual changes

The FDA's MedWatch safety alert tells patients to contact a health professional immediately if they develop sudden painless vision loss, missing areas of vision, color distortion or other visual disturbances. Clinicians should promptly refer suspected NAION cases to an ophthalmologist, a doctor specializing in eye disease.

If NAION develops, the FDA advises clinicians to consider stopping the GLP-1 medicine unless its treatment benefits clearly outweigh the risk. Taiwan's earlier semaglutide communication gives a more direct instruction to stop semaglutide when NAION is confirmed. Patients should discuss the decision with the clinician managing their treatment.

Dr. Joseph Rizzo, a specialist in disorders involving the eyes and nervous system at Massachusetts Eye and Ear and a coauthor of the 2024 semaglutide study, said vision loss from NAION is usually lasting, with limited recovery. He believes the evidence indicates increased risk, while continuing to recognize the medicines' benefits.

Rizzo explained why he does not discourage patients from using GLP-1 medicines:

The medicines have really been profoundly beneficial to a large number of people.

Some products have approved uses that extend beyond weight and blood sugar control, including reducing cardiovascular events or worsening kidney disease in specified groups. Certain medicines are also approved for obstructive sleep apnea or a form of liver disease. The relevant benefits vary by product and patient.

Company responses, legal claims and online sales

Novo Nordisk continues to express confidence in the balance between benefits and risks of its GLP-1 medicines and disputes a causal link with NAION. Eli Lilly says it is evaluating the FDA update and notes that the communication applies to all medicines with GLP-1 activity, without citing findings specific to Lilly products.

Patients have also pursued compensation and litigation. Nearly 100 lawsuits concerning NAION have been filed in New Jersey since 2025. At least 4,000 complaints involving alleged GLP-1 complications, including gastrointestinal injuries and vision loss, have been consolidated in federal and state proceedings. The companies contest allegations about their medicines' safety and warnings.

In Denmark, the Danish Patient Compensation body said four patients who lost vision after using Novo Nordisk GLP-1 medicines had received compensation. The U.S. labeling action, European safety findings and patient claims have placed the rare condition under closer scrutiny across several countries.

Taiwan is also targeting medicines sold outside authorized channels. The TFDA says it works with Meta to remove illegal sales posts, with the Taiwan Network Information Center to block unlawful websites, and with customs and other agencies to prevent unapproved products from circulating.

GLP-1 injections are prescription medicines in Taiwan. The agency urges people to obtain them after medical examination and professional assessment, follow prescribing instructions and avoid products bought through unauthorized websites or other informal channels. Suspected adverse reactions can be reported to Taiwan's national reporting center at 02-2396-0100.

Key Points

• The FDA requires NAION warnings for all GLP-1 receptor agonist medicines following its November 9, 2026, safety communication.
• Its clinical trial analysis found 6.4 cases per 100,000 person-years with GLP-1 medicines, compared with 3.8 with comparison treatments.
• Taiwan is expanding its safety assessment beyond semaglutide to the entire drug class.
• Taiwan received 63 suspected adverse reaction reports in 2026: 39 involving weight management and 24 involving diabetes treatment.
• Sudden painless vision loss, blind spots, blurred sight or color changes require immediate medical attention.
• Patients diagnosed with NAION should discuss continued treatment with their clinician, with prompt specialist eye assessment.