Peptide basics

What the approved GLP-1 labels actually warn about

This page reports which warnings appear in the FDA-approved labelling and how they are worded. It reproduces no instruction about amounts, schedules or administration, and it gives no advice about symptoms — that requires someone who can examine you.

Where these come from

US prescription labelling has a legally defined structure. 21 CFR 201.57 sets out what each section must contain, including a boxed warning where one is required, contraindications, and warnings and precautions. Everything on this page is read from the labelling itself, through the openFDA labelling endpoint, and linked to the corresponding published label.⁷⁸

The boxed warning, and how carefully it is worded

The Wegovy label's boxed warning states that in mice and rats semaglutide caused an increase in thyroid C-cell tumours after lifetime exposure at clinically relevant plasma exposures, and then states directly that it is unknown whether Wegovy causes thyroid C-cell tumours, including medullary thyroid carcinoma, in humans, because the human relevance of the rodent finding has not been determined.¹

The same section adds that cases of medullary thyroid carcinoma have been reported in the postmarketing period in patients treated with liraglutide, another GLP-1 receptor agonist, and that the data in those reports are insufficient to establish or exclude a causal relationship.¹

Zepbound's version is built identically for tirzepatide, citing a two-year rat study and stating that whether the product causes such tumours in humans is unknown. Mounjaro, Ozempic and Rybelsus, Saxenda and Trulicity carry the same warning for their own molecules.²³⁴⁵⁶

What the warnings section lists

Wegovy's warnings and precautions section lists acute pancreatitis, acute gallbladder disease, hypoglycaemia when used with insulin or an insulin secretagogue, acute kidney injury, hypersensitivity reactions including anaphylaxis and angioedema reported after marketing, diabetic retinopathy complications in patients with type 2 diabetes, heart rate increase, and suicidal behaviour and ideation.¹

Zepbound's section lists severe gastrointestinal adverse reactions, acute kidney injury due to volume depletion, acute gallbladder disease, acute pancreatitis, hypersensitivity reactions, hypoglycaemia when combined with insulin or an insulin secretagogue, diabetic retinopathy complications, and pulmonary aspiration during general anaesthesia or deep sedation.²

• The two lists overlap heavily but are not identical, and neither is a summary of the other.
• Some entries are worded as observed in clinical trials, some as reported postmarketing — a distinction the label makes and most secondary coverage drops.
• Some entries describe a situation rather than an event: the aspiration item concerns people undergoing procedures under anaesthesia.
• Some entries are about combinations: the hypoglycaemia item is specifically about concomitant use with certain other diabetes drugs.¹²

Warnings are not frequencies

A warnings entry says an event has been observed and should be watched for. It does not say how often it happens. The section that carries frequencies is the adverse reactions table, which prints percentages against a placebo column and the number of participants in each — a structure the warnings section does not have.¹⁷

The distinction matters because the events described in warnings are typically the uncommon ones. Pancreatitis and gallbladder disease appear in the warnings section precisely because they are serious and infrequent enough that a trial adverse-reaction table would not be the place a reader learns about them.¹⁹

Contraindications are the firm part

The contraindications section is shorter and much more definite. For Wegovy it is a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2, and a prior serious hypersensitivity reaction to semaglutide or the product's excipients. Zepbound's is the same pair for tirzepatide.¹²

Not every product in the class carries the same warnings

The twice-daily exenatide product, Byetta, carries no boxed warning in the labelling currently published. It is a GLP-1 receptor agonist marketed in the United States, so class membership does not by itself determine what appears at the top of a label.¹⁰

What determines it is the evidence assembled for that specific product and application, reviewed at approval and revised afterwards. Reading one label and generalising the result to a class is a mistake the labels themselves do not make.⁷¹⁰

Exenatide is the useful counterexample here: same receptor class, and a currently published US label without a boxed warning.

Common questions