What a peptide is
A peptide is a short chain of amino acids — the same molecular building blocks that link together to form proteins. The difference is mostly length: string a handful of amino acids together and you have a peptide; string hundreds and you have a protein. Your body makes peptides constantly and uses many of them as hormones and chemical messengers. GLP-1 — glucagon-like peptide-1 — is one of them, an incretin hormone your gut releases after you eat.
Why it matters if you’re on a GLP-1
This site’s whole subject is, quite literally, peptides. The medications people mean by “GLP-1 drugs” — semaglutide, tirzepatide, and their relatives — are engineered peptides: lab-made molecules modeled on the natural GLP-1 hormone but tweaked so the body can’t break them down quickly. That single design choice is why a drug based on a hormone that normally lasts minutes can instead work for a week. As receptor agonists, these peptides bind the same receptors your own GLP-1 uses. If you want the bigger picture of how they act, see the GLP-1 class overview.
What to keep in mind
Because peptides are delicate, form and handling matter. Most GLP-1s are injected because the gut would digest a swallowed peptide before it could work, and compounded or reconstituted products come with their own storage and mixing considerations. “Peptide” also gets used loosely in the supplement and research world for products that aren’t approved medications — so it’s worth knowing exactly what you’re looking at, and getting anything you take through a legitimate prescriber and pharmacy.