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Safety communication

FDA safety communication: tirzepatide and thyroid C-cell tumors

Tirzepatide (Zepbound / Mounjaro) · Announced 2026-02-20 · Last reviewed May 2026

Reviewed by the glpzoom Editorial Team against primary clinical sources — FDA labeling, peer-reviewed trials, and specialty-society guidelines.
Content current as of May 2026; updated when guidance or availability changes.

In February 2026 the FDA issued a safety communication reiterating the existing tirzepatide black-box warning regarding thyroid C-cell tumor risk based on rodent studies. The communication followed a small uptick in MedWatch reports of medullary thyroid carcinoma diagnoses in tirzepatide users; the FDA emphasized that causation has not been established (the underlying baseline rate of MTC in the general population is itself low, and confounding by patient history is significant). The agency confirmed that the tirzepatide prescribing information was not being updated and reaffirmed the existing contraindication in patients with personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN2).

What's affected

  • All tirzepatide products: Zepbound, Mounjaro, compounded tirzepatide

What patients should do

  1. If you have personal or family history of MTC or MEN2, you should not be taking tirzepatide — confirm with your prescriber
  2. Report any neck swelling, persistent hoarseness, or difficulty swallowing to your prescriber promptly
  3. No action needed for patients without MTC/MEN2 risk factors who tolerate the medication

Primary sources

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