GLP-1 Boxed Warnings: What the Label Actually Says

Nausea and GI upset get most of the attention because they're the side effects people actually feel. The boxed warning and the rarer safety signals get less coverage precisely because they're rare — but "rare" isn't the same as "you don't need to know about it before you start." Here's the exact language from the current FDA labels for the four GLP-1 obesity and diabetes brands, plus the European regulator’s subsequent assessment of the rare eye condition NAION.

The boxed warning: thyroid C-cell tumors

Every major GLP-1 label — Ozempic, Wegovy, Mounjaro, and Zepbound — carries the same boxed warning, the FDA's highest-visibility safety alert. Ozempic's label states it plainly: "In rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. It is unknown whether OZEMPIC causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans as human relevance of semaglutide-induced rodent thyroid C-cell tumors has not been determined"¹. Mounjaro and Zepbound carry near-identical language for tirzepatide². The key phrase is "human relevance... has not been determined" — this is a warning based on an animal signal that hasn't been confirmed or ruled out in people, which is exactly why it's a boxed warning rather than a settled fact. All four labels are unambiguous on one point that isn't ambiguous: every one of these drugs "is contraindicated in patients with a personal or family history of MTC or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)"¹². If that's your history, this isn't a drug to negotiate around — it's a hard no, and your prescriber needs to know before you start, not after.

Acute pancreatitis

Beyond the boxed warning, Wegovy's label states: "Acute pancreatitis, including fatal and non-fatal hemorrhagic or necrotizing pancreatitis, has been observed in patients treated with GLP-1 receptor agonists, including WEGOVY"³. This is a class-wide warning, not specific to one molecule. The label doesn't quantify a precise incidence rate, but it does instruct discontinuing the drug if pancreatitis is suspected and not restarting if it's confirmed.

Gallbladder disease

Rapid weight loss from any cause raises gallstone risk, and GLP-1s are no exception. Wegovy's label states directly: "Treatment with WEGOVY is associated with an increased occurrence of cholelithiasis and cholecystitis"³ — gallstones and gallbladder inflammation, respectively. We cite the specific trial incidence rate (1.6% of Wegovy-treated adults) in GLP-1 side effects: what the STEP and SURMOUNT trials actually reported; this section is about the label's warning language, not just the number — for the full pooled-trial risk picture across 76 studies, see GLP-1 and gallbladder disease: what the meta-analysis of 76 trials shows.

NAION: the European regulator has reviewed the evidence

NAION is sudden optic-nerve damage from reduced blood flow. In June 2025, the European Medicines Agency's safety committee concluded that it is a very rare side effect of semaglutide and recommended updating the product information for Ozempic, Rybelsus and Wegovy⁵. EMA describes the frequency as up to 1 in 10,000 treated people. Its review of large epidemiological studies estimated about one additional case per 10,000 person-years of treatment. A person-year is one person treated for a year; these figures are not interchangeable with a selected clinic's cumulative incidence.

A 2024 observational study had raised the initial concern, but its referral-clinic population cannot provide a general patient's absolute risk⁴. The current discussion should include the later regulator review, not stop at that first association. The EMA conclusion is a European regulatory finding; it is not a claim that FDA added a U.S. boxed warning.

Sudden vision loss or rapidly worsening eyesight needs urgent medical assessment. EMA advises contacting a doctor without delay and stopping semaglutide if NAION is confirmed⁵. See our GLP-1 lawsuit explainer for the separate litigation context.

None of this is a reason to panic — it's a reason to disclose

A boxed warning and a rare safety signal both function the same way in practice: they're things your prescriber needs on record before you start, not reasons to assume the drug isn't right for you. A program with a thin intake that never asks about your personal or family thyroid history, your vision, or prior pancreatitis is skipping exactly the questions these warnings exist to prompt — the same concern we raise about disclosure generally in GLP-1 drug interactions: what to tell your prescriber. Mental health history belongs on that same disclosure list; see does Ozempic cause depression? What the evidence actually shows for the FDA’s completed January 2026 review and its finding of no increased risk of suicidal behavior or ideation.

Where this fits your provider decision

Discuss the label warnings and your personal and family medical history with the prescribing clinician. Our Value Score methodology covers price and program terms; it does not certify clinical screening. The provider reviews and semaglutide and tirzepatide rankings help compare published costs after that clinical discussion.

This piece sits in our research index alongside every other sourced explainer we publish — the trials, the compounding rules and the pricing mechanics, grouped by the question each one answers.