A rare thyroid cancer arising from the thyroid's C cells; a personal or family history of it is a contraindication to GLP-1 medications.
Updated Jul 18, 2026
Medullary thyroid carcinoma (MTC) is a rare form of thyroid cancer that arises from the thyroid's C cells. It is the reason GLP-1 medication labels carry a boxed warning, based on findings that some of these drugs caused thyroid C-cell tumors in rodents; whether the same risk applies to humans has not been established.
A personal or family history of MTC, or of the inherited syndrome MEN 2, is listed as a contraindication to GLP-1 receptor agonists.
Lipohypertrophy — A rubbery lump of thickened fatty tissue under the skin caused by repeated injections in the same spot.
DPP-4 — Dipeptidyl peptidase-4, the enzyme that rapidly breaks down the body's own GLP-1 within minutes.
Related guides
Safe sharps disposal for GLP-1 injectors — Every GLP-1 injection ends with a needle you have to put somewhere. Here's the FDA's two-step system: a proper sharps container (or an acceptable heavy-duty household stand-in), the short list of things never to do with a used needle, how to find your community's disposal rules, and what changes when you travel.
Reading an insulin syringe: units, mL, and mg for compounded GLP-1 doses — U-100 insulin syringes mark volume in "units" — 100 per mL — and your vial's concentration is what converts a prescribed mg dose into a unit count. This walkthrough teaches the arithmetic with worked examples at different concentrations, explains the FDA-documented error patterns, and gives a verify-with-your-pharmacist checklist. It teaches reading the syringe; it does not prescribe doses.
GLP-1s with insulin or sulfonylureas: understanding hypoglycemia risk — A GLP-1 on its own rarely causes low blood sugar, but pairing it with insulin or a sulfonylurea meaningfully raises the risk — here's why, how to recognize hypoglycemia, and what to settle with your prescriber before any dose changes.