GLP-1 drug side effects are drawing increased attention as patients, doctors and regulators sort through reports of rare but serious harms linked to popular diabetes and weight-loss medications.
Todd Engel, a longtime heavy-equipment operator from suburban Maryland, began using Ozempic, a GLP-1, in early 2023 for diabetes. On New Year’s Eve that winter, he awoke with vision loss in his right eye, describing it as total darkness. A physician diagnosed nonarteritic anterior ischemic optic neuropathy, or NAION, an inoperable condition tied to small strokes that cut off blood flow to the optic nerve. When Engel’s wife, Shelley, asked whether Ozempic could be a factor, she recalls being told there was no information suggesting that.
About seven months later, research in JAMA Ophthalmology reported higher rates of NAION among diabetic patients taking Ozempic, known generically as semaglutide. Engel and his doctor did not know about the findings at the time, and Engel continued weekly injections until vision in his left eye also went dark.
Growing scrutiny of GLP-1 drug side effects
Use of these medicines is widespread. A recent national analysis found more than one in 10 Americans are currently taking a GLP-1 drug for weight loss, and one in seven have used them at some point. Prescriptions now span a range of conditions and come with side effects that vary from mild gastrointestinal symptoms to more serious complications.
Engel has sued Novo Nordisk, alleging the company failed to warn about the risk of NAION. His case is among two main consolidated lawsuits that claim life-threatening or life-altering injuries from GLP-1 drugs.
Novo Nordisk, in a statement, cited subsequent research questioning whether its GLP-1 causes NAION and said the cases lack merit.
The legal debate turns on whether the drugs caused the injuries. Observational studies can reveal correlations, such as higher rates of an eye condition among users, but they cannot establish causation without more rigorous investigation.
A partial database
The Food and Drug Administration maintains an adverse-events database where clinicians, patients and drugmakers can submit reports of possible complications. Reporting is largely voluntary and the agency does not verify submissions, but the system can flag issues for deeper review and potential label changes.
Since 2024, more than 1,000 reports of optic neuropathy associated with GLP-1s appear in the database, out of nearly 190,000 reports related to these drugs, most involving milder issues like gastrointestinal upset, dosing mistakes or injection-site reactions.
Novo Nordisk, which makes Ozempic and Wegovy, says NAION and other serious events have been exceedingly rare in clinical trials and that it continues to share post-market safety data with the FDA. The agency has not requested label changes. In an email, the FDA said it has launched its own study to assess NAION risk and will determine whether regulatory action is needed after its review.
The legal challenge
Attorney Jonathan Orent, a lead court-appointed lawyer in two multi-district litigations alleging GLP-1 harms, argues manufacturers should strengthen warnings to physicians and patients, similar to actions taken in Europe, even if the events are very rare.
He contends that clinical trials are not large or diverse enough to reliably detect rare events. His cases include 247 plaintiffs reporting NAION and more than 4,000 alleging serious digestive problems such as pancreatitis or gallstones. Eli Lilly, which markets tirzepatide under the brands Mounjaro and Zepbound, said it will vigorously defend against these claims.
An analysis of FDA adverse-events data shows 1,928 reports of pancreatitis since 2024, along with other pancreatitis types, including 135 cases of necrotizing pancreatitis.
Engel says he would have stopped using Ozempic if he had known about a possible blindness risk. He describes profound losses, from giving up work to no longer being able to walk the beach unaided. He also grieves the inability to see his wife’s face and play with his grandchildren.
Uncertainty in reporting
Obesity and diabetes affect multiple organs and elevate risks for other illnesses, which complicates efforts to determine whether GLP-1 drug side effects are directly caused by the medicines. Emory University diabetes specialist Mohammed Ali said he did not file FDA adverse-event reports for three patients who developed serious issues such as pancreatitis or gallstones while on GLP-1s, because he was not certain the drugs caused the problems.
Ali noted that some patients may have had undiagnosed conditions beforehand, which makes attribution difficult.
Calls to poison control
The surge in online sales and social media marketing adds more complexity, said Robert Miller, a pharmacist at the West Texas Poison Control Center. He said purchases through platforms like Instagram are a newer trend, often with minimal medical oversight, and poison-control centers are receiving more calls about vomiting and other GLP-1 side effects.
Miller questioned whether patients buying online have a physician engaged enough to report adverse effects, or someone they trust to notify about problems.
For now, these questions are playing out in court as plaintiffs seek damages. Shelley Engel also wants clearer warnings about potential side effects, which she believes could have helped her husband avoid blindness. “This could have been prevented, if we only knew,” she said.
Increased concern about prescription drug risks has come as more people seek medical and wellness shortcuts at home, from weight-loss medications to compact equipment like Bowflex SelectTech dumbbells.
