GLP-1 Vision Loss (NAION) Lawsuit

What Is the GLP-1 Vision Loss (NAION) Lawsuit About?

The GLP-1 vision loss lawsuit is a new and rapidly growing mass tort litigation alleging that popular weight-loss and diabetes medications — including Ozempic, Wegovy, Mounjaro, and Zepbound — are linked to NAION (non-arteritic anterior ischemic optic neuropathy), a serious condition that causes sudden, often permanent vision loss. The cases are consolidated in MDL 3163 in the Eastern District of Pennsylvania under Judge Karen S. Marston, created in December 2025.

This lawsuit is separate from the existing Ozempic/Wegovy stomach paralysis litigation (MDL 3094), which addresses gastroparesis and gastrointestinal complications. The NAION vision loss litigation focuses on a different and equally serious alleged injury: damage to the optic nerve causing sudden, irreversible vision loss.

The lawsuit was sparked by a landmark July 2023 study by researchers at Harvard Medical School and Mass General Brigham that found patients taking semaglutide (the active ingredient in Ozempic and Wegovy) had a dramatically higher rate of developing NAION: 4 times higher for diabetic patients and 7.6 times higher for overweight/obese patients compared to those on other treatments. As of February 2026, over 2,947 lawsuits have been filed, with 37 pending in the MDL.

Plaintiffs allege that Novo Nordisk and Eli Lilly knew or should have known about the NAION risk from clinical trial data and post-marketing surveillance but failed to adequately warn patients and prescribing physicians. For related litigation, see our pages on the Ozempic stomach paralysis lawsuit and the Depo-Provera brain tumor lawsuit.

What Is NAION (Non-Arteritic Anterior Ischemic Optic Neuropathy)?

NAION is the most common acute optic neuropathy in adults over 50. It occurs when blood flow to the anterior (front) portion of the optic nerve is disrupted, damaging the nerve fibers that transmit visual information from the eye to the brain. The result is sudden, painless vision loss — usually noticed upon waking — that is often permanent.

NAION typically affects one eye at a time. Patients usually notice a sudden loss of vision in the affected eye — often described as a dark area or shadow in part of the visual field, typically in the lower half. The vision loss is usually painless, which distinguishes NAION from other causes of acute vision loss. While some patients may experience partial recovery in the weeks following the event, most are left with permanent visual deficits. There is currently no proven treatment to restore vision lost to NAION.

The connection between GLP-1 medications and NAION is alleged to involve changes in blood flow dynamics, blood pressure, and vascular supply to the optic nerve. The exact mechanism is still being researched, but the statistical correlation identified in the Harvard study is significant.

Which GLP-1 Drugs Are Involved?

The lawsuit covers the same class of GLP-1 receptor agonist medications involved in the separate gastroparesis litigation, but the alleged injury is different — vision loss rather than stomach paralysis:

The Harvard study specifically examined semaglutide (the active ingredient in Ozempic, Wegovy, and Rybelsus) and found the elevated NAION risk. Tirzepatide (Mounjaro, Zepbound) is also named in the lawsuit based on its similar mechanism of action as a GLP-1 receptor agonist, though studies specific to tirzepatide and NAION are ongoing.

Harvard Study: NAION Risk Data

The most significant piece of scientific evidence in this litigation is the July 2023 study by researchers at Harvard Medical School and Massachusetts General Hospital (Mass General Brigham health system). The study examined medical records of patients prescribed semaglutide and compared their NAION rates to matched controls:

The Harvard study controlled for known NAION risk factors including diabetes, hypertension, sleep apnea, and other conditions. Even after adjusting for these confounders, the elevated NAION risk in semaglutide users remained statistically significant. This is critical because it suggests the NAION risk is attributable to the medication itself, not simply to the underlying conditions being treated.

Who Qualifies for the GLP-1 Vision Loss Lawsuit?

You may qualify to file a claim in the GLP-1 vision loss lawsuit if you used a GLP-1 medication and developed NAION or other sudden vision loss. Each case is evaluated individually by an attorney:

Lawsuit Timeline

The GLP-1 vision loss litigation is one of the newest mass torts in the federal court system. Here are the key milestones from drug approval through MDL creation:

Settlement Amounts and Projections

As of early 2026, no settlements have been reached in the GLP-1 NAION litigation — MDL 3163 was only created in December 2025. The cases are in the earliest stages of discovery. However, because vision loss is typically permanent and profoundly impacts quality of life, legal analysts project that individual settlement values could be significant:

The permanence of NAION-related vision loss is a critical factor in potential compensation. Unlike some injuries that may heal, optic nerve damage is irreversible with current medical technology. Settlement amounts will likely be shaped by the extent of vision loss (partial vs. total), whether one or both eyes are affected, the impact on the claimant's ability to work and perform daily activities, and bellwether trial outcomes. For general information, see our guide on mass tort settlement amounts.

How to File a GLP-1 Vision Loss Claim

If you experienced sudden vision loss or were diagnosed with NAION while taking a GLP-1 medication, here is the process for pursuing a legal claim:

For more detailed information about the legal process, read our guide on how to join a mass tort lawsuit. To understand the MDL process in which your case will be handled, see our guide on what is an MDL (multidistrict litigation).

Named Defendants

The GLP-1 vision loss lawsuit names the same pharmaceutical companies as the gastroparesis litigation:

• Novo Nordisk A/S — The Danish pharmaceutical giant that manufactures Ozempic, Wegovy, and Rybelsus (all containing semaglutide). Novo Nordisk is the primary defendant because the Harvard study specifically identified semaglutide as associated with elevated NAION risk. The company's revenue from GLP-1 products exceeded $20 billion in recent years, making these among the most commercially successful drugs in pharmaceutical history.
• Eli Lilly and Company — The American pharmaceutical company that manufactures Mounjaro and Zepbound (both containing tirzepatide). Eli Lilly is named as a defendant because tirzepatide is a GLP-1 receptor agonist with a similar mechanism of action, and plaintiffs allege the NAION risk is a class-wide effect of GLP-1 drugs.

Plaintiffs allege that both companies had access to clinical trial data and post-marketing safety surveillance data that should have alerted them to the NAION risk, and that they failed to update drug labeling with adequate warnings. The discovery phase of MDL 3163 will focus on what these companies knew about NAION risk and when they knew it. For related litigation involving the same companies, see our Ozempic stomach paralysis lawsuit page.

Scientific and Medical Evidence

The scientific evidence supporting the GLP-1/NAION connection is anchored by the Harvard study but extends to other data sources:

• Harvard/Mass General Brigham Study (July 2023): Published in JAMA Ophthalmology, this retrospective matched cohort study found that diabetic patients on semaglutide had a 4x higher NAION rate (8.9% vs. 1.8%), and overweight patients on semaglutide had a 7.6x higher NAION rate compared to those on other treatments. The results were statistically significant and controlled for known NAION risk factors.
• FDA adverse event reports: Reports of NAION and vision loss in GLP-1 users have been filed with the FDA's FAERS (Adverse Event Reporting System) database. The FDA initiated a review of the NAION safety signal in 2024.
• Biological plausibility: GLP-1 medications affect blood pressure regulation and vascular function. NAION is caused by disrupted blood flow to the optic nerve. Researchers hypothesize that GLP-1 drugs may alter the vascular dynamics in the small blood vessels supplying the optic nerve, particularly during blood pressure dips that occur during sleep (which is when most NAION events occur).
• Clinical trial data review: Discovery in MDL 3163 will seek to determine whether clinical trial data submitted to the FDA for drug approval contained signals of NAION or vision-related adverse events that were not flagged or disclosed.
• Additional published research: Following the Harvard study, additional researchers have begun investigating the GLP-1/NAION connection. This growing body of literature will form an important part of the scientific evidence in the litigation.
• Drug labeling history: The absence of NAION warnings on GLP-1 drug labels despite the emerging evidence is a central allegation. Plaintiffs argue that adequate labeling would have alerted ophthalmologists and prescribing physicians to monitor for visual symptoms.

For a broader understanding of how these cases proceed, see our guide on how mass tort lawsuits work. For information about other pharmaceutical lawsuits involving inadequate warnings, see our page on the Tepezza hearing loss lawsuit.