Brand-name medications are made by the drug maker and approved by the FDA, with a fixed formulation, labeling and manufacturing checks.
Compounded medications are prepared by a pharmacy, for example as vials of semaglutide or tirzepatide. The FDA says compounded drugs are not FDA-approved and that it does not review them for safety, effectiveness or quality before they are marketed. It has also reported adverse events, some requiring hospitalization, that may be linked to dosing errors with compounded injectable semaglutide.
Compounding of copies of these medications was widespread while they were in shortage. The FDA declared the tirzepatide shortage over in December 2024 and the semaglutide shortage over in February 2025, which changed the rules for compounding them.
Whether a medication is right for you, and where it comes from, is something to discuss with your prescriber and pharmacist. If you use a vial, the mixing & syringe converter shows the math from mg to syringe units.
Sources: FDA, concerns with unapproved GLP-1 drugs used for weight loss and policies for compounders as GLP-1 supply stabilizes.