Todd Engel had spent four decades operating heavy machinery in suburban Maryland. Now, after losing sight in both eyes, he says he can no longer work or walk along the beach without help. Engel began taking Ozempic for diabetes in early 2023. On New Year’s Eve that year, he woke up unable to see out of his right eye. Doctors diagnosed nonarteritic anterior ischemic optic neuropathy, or NAION, a condition involving reduced blood flow to the optic nerve. Engel says his left eye went dark about a year later, while he was still taking the medication. He and his wife, Shelley, say they were not told of a possible connection between Ozempic and NAION. Engel has sued Novo Nordisk, alleging the company failed to adequately warn patients and doctors. The company says the claims lack merit and points to later research that it says casts doubt on a causal link. A 2024 study in JAMA Ophthalmology found higher rates of NAION among diabetic patients taking semaglutide, the active ingredient in Ozempic. But the American Academy of Ophthalmology and the North American Neuro-Ophthalmology Society cautioned that the study could show an association, not prove the drug caused the condition. The groups said more research is needed and did not recommend that patients stop taking GLP-1 drugs. The dispute is part of two consolidated lawsuits alleging serious harms linked to GLP-1 medications. A court-appointed attorney for plaintiffs said the cases include 247 people with NAION and more than 4,000 with other serious digestive conditions, including pancreatitis and gallstones. Eli Lilly, which makes the GLP-1 drugs Mounjaro and Zepbound, said it would vigorously defend against the claims. Federal safety data offer one signal of possible problems, but not a reliable count of how often they occur. The Food and Drug Administration’s adverse-event database includes more than 1,000 reports of optic neuropathy involving GLP-1 drugs since 2024, out of nearly 190,000 reports about the drugs overall during that period. The reports are mostly voluntary and are not verified by the agency, so they cannot establish that a medication caused a reported condition or show its rate among all patients. The database also recorded 1,928 pancreatitis reports since 2024, including 135 reports of necrotizing pancreatitis. Novo Nordisk says serious conditions such as NAION were exceedingly rare in clinical trials and that it continues to share post-market safety data with the FDA. The agency says it is studying NAION risk and will consider whether regulatory action is needed after its assessment is complete. Doctors say it can be difficult to determine whether a complication stems from a drug or from an underlying illness. Mohammed Ali, a diabetes specialist at Emory University, said he did not report three patients’ serious problems, including pancreatitis or gallstones, because he could not be sure the drugs caused them. Diabetes and obesity themselves can increase the risk of health problems affecting multiple organs. The growth of online GLP-1 sales may further complicate monitoring, said Robert Miller, a pharmacist with the West Texas Poison Control Center. Some online sellers provide little medical supervision, and poison-control centers are hearing from patients reporting symptoms such as vomiting. For Engel, the uncertainty does not lessen the consequences. He says he would have stopped taking Ozempic if he had known of a possible risk to his vision. He can no longer play ball with his grandchildren or see his wife’s face. Shelley Engel says stronger warnings might have changed what happened to her husband.