Weight-Loss Drugs Face Lawsuits Over Vision Loss
Popular weight-loss and diabetes medications including Ozempic, Wegovy, Mounjaro and Zepbound are facing a growing number of lawsuits from patients who allege that the drugs caused a rare form of vision loss known as nonarteritic anterior ischemic optic neuropathy, or NAION.
NAION is sometimes described as an “eye stroke.” It occurs when blood flow to the optic nerve is reduced, potentially causing sudden vision loss. The condition most commonly affects people over age 50 and can result in permanent impairment. The lawsuits allege that drugmakers failed to adequately warn patients about a possible connection between their medications and NAION.
The litigation primarily involves drugs made by Novo Nordisk and Eli Lilly. Novo Nordisk produces Ozempic and Wegovy, both of which contain semaglutide. Eli Lilly makes Mounjaro and Zepbound, which contain tirzepatide.
According to reporting on the lawsuits, dozens of patients have filed personal-injury claims against the manufacturers. Some lawsuits have been filed in federal court, while more than 90 cases against Novo Nordisk have reportedly been filed in New Jersey state court since 2025 by one law firm representing patients who developed NAION while taking the company’s medications.
The allegations are part of a much larger wave of litigation involving GLP-1 medications. Patients have filed separate lawsuits concerning other alleged injuries and side effects, making the vision-loss claims another area of legal scrutiny for a rapidly expanding class of medicines.
NAION itself is rare. It typically causes sudden, painless vision loss in one eye, although symptoms can include blurred or dim vision, loss of peripheral vision and changes in color perception. There is currently no proven treatment that reverses the optic-nerve damage caused by NAION, although some patients may experience partial recovery.
The scientific evidence concerning GLP-1 medications and NAION remains unsettled. Some observational studies have identified a possible increased risk, particularly among people taking semaglutide. A 2025 analysis involving millions of adults found a modestly elevated risk of NAION among semaglutide users compared with people taking another class of diabetes medication. A 2024 study from researchers associated with Harvard Medical School also reported a substantially higher relative risk among some semaglutide users.
Those findings, however, do not establish that semaglutide caused the eye condition. Observational studies can identify associations but cannot necessarily separate the effects of a drug from underlying medical conditions. That distinction is particularly important because many people taking GLP-1 drugs have diabetes, obesity, high blood pressure or sleep apnea — conditions that themselves can affect the risk of NAION.
Other research has not found the same association. Novo Nordisk has pointed to company-funded research that found no increased risk of NAION among people taking its GLP-1 medicines. The company has characterized the U.S. lawsuits as without merit and said it is vigorously defending them.
Eli Lilly has likewise disputed the suggestion that its medications have been shown to cause NAION. The company has said it continues to monitor safety information and that available evidence does not establish a causal relationship between its medicines and the condition.
Regulators have taken different approaches as evidence continues to develop. The U.S. Food and Drug Administration has been reviewing available information about a possible association between semaglutide and NAION but has not concluded that semaglutide causes the condition or required a corresponding warning on U.S. labels.
European regulators have taken a more cautious position. The European Medicines Agency determined that there was sufficient evidence of a possible association to recommend adding NAION as a very rare adverse reaction to information for semaglutide medicines. Novo Nordisk subsequently updated European labeling for Ozempic and Wegovy to identify the potential risk.
The European assessment does not mean that regulators have determined the drugs cause NAION in individual patients. Rather, it reflects a determination that the available evidence warranted communicating the potential risk to patients and healthcare professionals.
The lawsuits therefore face an important causation question. Individual plaintiffs will generally need to establish that their injuries were connected to the drugs and that the manufacturers had legal duties concerning warnings about the alleged risk. The companies, meanwhile, can challenge both the scientific evidence and the legal claims that their warnings were inadequate.
The issue is particularly significant because GLP-1 drugs have become widely used. Their popularity has expanded rapidly as medications such as Wegovy and Zepbound have become major treatments for obesity, while Ozempic and Mounjaro are widely prescribed for type 2 diabetes. Millions of Americans are now using GLP-1 medications.
The growth of the market also means that even a very rare adverse event can affect a substantial number of people. At the same time, the rarity of NAION makes it difficult to determine whether an apparent increase among GLP-1 users reflects the medications themselves or the underlying health characteristics of the patients receiving them.
The litigation comes as access to these medications is also expanding. A new Medicare pilot program launched in 2026 offers eligible beneficiaries access to certain GLP-1 weight-loss treatments at a $50 monthly copay. That development could substantially increase the number of older Americans receiving the medications, making ongoing safety monitoring particularly important.
The current legal cases have not produced a final judicial finding that Ozempic, Wegovy, Mounjaro or Zepbound cause NAION. The allegations remain claims made by plaintiffs, while the drugmakers dispute them and point to scientific evidence that they say does not establish causation.
For patients and physicians, the emerging dispute highlights the importance of distinguishing between a potential safety signal and a confirmed drug-related risk. NAION is a recognized medical condition with established risk factors, and the presence of those risk factors can complicate attempts to determine whether a medication contributed to an individual case.
The lawsuits will now proceed alongside continuing scientific and regulatory review. Future research, regulatory decisions and court rulings could provide greater clarity about whether there is a causal relationship between GLP-1 medications and NAION and, if so, how significant the risk may be.
For now, the most established facts are that NAION is rare and potentially permanent, some research has identified a possible association with semaglutide, other research has not established the same relationship, regulators are continuing to assess the evidence, and patients have filed lawsuits alleging inadequate warnings.
Key Legal Outcome
- Dozens of patients have filed lawsuits against Novo Nordisk and Eli Lilly alleging GLP-1 drugs caused NAION-related vision loss.
- Plaintiffs contend the manufacturers failed to adequately warn patients about the potential risk.
- The lawsuits involve Ozempic, Wegovy, Mounjaro and Zepbound.
- Novo Nordisk and Eli Lilly dispute the allegations and say existing evidence does not establish that their medicines cause NAION.
- No court has established that GLP-1 medications caused the plaintiffs’ vision loss.
Why It Matters
- NAION can cause sudden and potentially permanent vision loss, making the alleged safety issue significant for patients.
- The litigation could eventually affect labeling, warnings and liability for major GLP-1 manufacturers.
- Scientific evidence remains mixed, with some observational studies suggesting an association and others failing to establish one.
- The FDA is reviewing the possible association, while European regulators have recommended a warning for semaglutide.
- The expanding number of GLP-1 users means regulators and researchers will have a larger population from which to monitor rare adverse events.
