Todd Engel took Ozempic to treat his type 2 diabetes. Today he is legally registered as blind. A nurse who began weight loss treatment woke up one morning with no vision in her right eye. A man in California lost his wife, who suffered episodes of violent vomiting that led to fatal complications. These are not made-up stories: they are cases captured in lawsuits that more than 4,000 Americans have filed against Novo Nordisk, the Danish maker of Ozempic and Wegovy, and against Eli Lilly, maker of Mounjaro.
All of the plaintiffs share a central allegation: They were never adequately warned about the serious side effects that now affect their lives. According to their statements to The Independent, if they had known those risks, they would never have considered using these medications. The question the cases raise is not whether GLP-1 drugs are effective—there is strong evidence that they are for the approved indications—but whether the extent of their adverse effects was communicated clearly enough to patients and prescribers.
The known effects and those that science has just discovered
The most common documented side effects of GLP-1 drugs are gastrointestinal: nausea, vomiting, diarrhea, constipation. These effects are bothersome but generally manageable and reduce with time and dose adjustment. The most serious, which appear in the package inserts, include pancreatitis, possible thyroid tumors and an increased risk of intestinal obstruction (paralytic ileus), especially in patients who will undergo general anesthesia.
But there are lesser-known effects that the scientific community is beginning to investigate after millions of people have started using them. A study by researchers at the University of Maryland, with first author Neil Sehgal, analyzed spontaneous reports of adverse effects from GLP-1 users and found worrying signs in several areas. Nearly 4% of users reported menstrual irregularities—a figure that would be even higher in an all-female sample, the authors note. And there are signs in hormonal disorders and changes in thermal regulation that scientists describe as a "signal that deserves to be studied."
GLP-1 adverse effects — What we know and what is being investigated
- Common (documented): nausea, vomiting, diarrhea, constipation, reflux
- Serious (documented in package inserts): pancreatitis, possible thyroid tumors, intestinal obstruction
- Risk under regulatory review: AION (non-arteritic anterior ischemic optic neuropathy) — vision loss
- Emerging signal in observational studies: menstrual irregularities (~4% users)
- Under investigation: impact on muscle mass, bone health, fertility
- Long-term cardiovascular risk in non-diabetics: no sufficient data yet
The case of vision loss deserves special attention. The condition that appears in several of the plaintiffs' testimonies is AION (non-arteritic anterior ischemic optic neuropathy), an alteration of blood flow to the optic nerve that can cause permanent vision loss. A study published in JAMA Ophthalmology in 2024 already identified a statistical association between semaglutide use and an increased risk of AION, especially in patients with type 2 diabetes and in those using the drug to lose weight without diabetes. The FDA is studying that signal, and the EMA has asked manufacturers to provide additional data.
The debate on risk communication
The central issue of the lawsuits—whether manufacturers adequately informed prescribers and patients of the risk—is what will define their legal outcome. Manufacturers argue that the package inserts include the warnings required by regulatory agencies, and that the risk-benefit ratio for the approved indications is favorable. The plaintiffs argue that risk communication in clinical practice was insufficient, that doctors and patients were not fully aware of the possibility of serious effects, and that some effects such as the risk of vision loss were not sufficiently highlighted.
The debate is not whether Ozempic works—it clearly works—but whether the patients who took it really knew what risks they were taking. That question has legal, ethical and public health consequences.
The rebound effect when treatment is stopped adds another dimension to the debate. Studies consistently show that most of the weight lost is regained in the months after stopping the drug. That makes GLP-1 open-ended treatments for most obese patients, not finite treatment courses. The economic implications for the health systems that could finance these drugs, and for the patients who would have to pay for them for life, are enormous and are rarely discussed with the same prominence as the spectacular weight loss rates.
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