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 what a 2024 observational study found about a signal none of the labels currently carry.

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.

A newer signal the labels don't carry yet: NAION

In 2024, a retrospective cohort study looked at nonarteritic anterior ischemic optic neuropathy (NAION) — a form of sudden vision loss from reduced blood flow to the optic nerve — in patients prescribed semaglutide, compared with patients on non-GLP-1 medications for the same underlying conditions⁴. Among patients with type 2 diabetes, the 36-month cumulative incidence of NAION was 8.9% in the semaglutide group versus 1.8% in the comparison group (hazard ratio 4.28)⁴. Among patients being treated for overweight or obesity, the gap was larger still: 6.7% versus 0.8% (hazard ratio 7.64)⁴. The study's own authors were careful about what this does and doesn't prove: "This study's findings suggest an association between semaglutide and NAION. As this was an observational study, future study is required to assess causality"⁴. An association in an observational study is not the same as a proven cause — but it's also not nothing, and as of this writing it hasn't yet been added as a formal warning to the semaglutide labels, which is exactly why an evidence-based source needs to cover it even though the label doesn't.

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.

Where this fits your provider decision

We score real medical oversight — not just a prescription rubber-stamp — as part of our Value Score methodology. Check how thorough each program's intake is in our provider reviews, and compare pricing on our semaglutide and tirzepatide boards once you've confirmed the medical process actually screens for this.

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.