Drug facts

The boxed warning

Reviewed August 2026

Quick answer

Tirzepatide carries a boxed warning — the strongest warning FDA applies — about the risk of thyroid C-cell tumors. It is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma, or with Multiple Endocrine Neoplasia syndrome type 2.

What the warning is based on1

The finding is in rats, where tirzepatide caused thyroid C-cell tumors in a way that depended on both dose and how long treatment continued, at exposures relevant to human use. Whether the same happens in people is unknown: the label states plainly that the human relevance of the rodent finding has not been determined.

That uncertainty is the reason for the warning rather than an argument against it. It is a known unknown carried forward into the label.

Contraindications1

  • Personal or family history of medullary thyroid carcinoma — a family history counts, not only your own.
  • Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
  • Known serious hypersensitivity to tirzepatide or to any of the excipients in the product.

The label also directs that patients be counselled about symptoms of thyroid tumors — a mass in the neck, difficulty swallowing, shortness of breath, or persistent hoarseness.

This applies to compounded preparations too1

The warning attaches to tirzepatide, the molecule, not to a particular manufacturer’s packaging of it. A compounded preparation is not exempt from it, and a seller that does not display it has not removed the risk — only the notice.

Whether any of this applies to you is a conversation with a prescriber. See the medical disclaimer.

Sources

  1. FDA prescribing information for ZEPBOUND (tirzepatide), boxed warning and section 4, revision 4/2026 DailyMed