Boxed Warning
The FDA's most serious label warning — GLP-1 weight drugs carry one about thyroid C-cell tumors seen in rodent studies.
A boxed warning (colloquially "black box") is the strongest caution the FDA places in prescribing information, reserved for risks that are serious or life-threatening. Semaglutide and tirzepatide share one: in rodent studies these drugs caused thyroid C-cell tumors, and it is not known whether they cause medullary thyroid carcinoma (MTC) in humans.
The warning translates into a hard screening rule — do not use these medications with a personal or family history of MTC or MEN 2 syndrome — which is precisely what a legitimate telehealth consultation asks about before prescribing. A boxed warning is not a prohibition for everyone; it's the system flagging who must not take the drug and what everyone else's prescriber should weigh.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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