What it means
Cells in your small intestine release GLP-1 when food arrives. It nudges the pancreas to release insulin when blood sugar is high, lowers glucagon, slows how fast your stomach empties and acts on appetite centers in the brain.
Your own GLP-1 is broken down within minutes by an enzyme called DPP-4. Drugs like semaglutide and tirzepatide are built to resist that breakdown, so they work for days instead of minutes. That longer action is why a once-weekly shot can change hunger and fullness all week.
When people say "a GLP-1," they usually mean a GLP-1 receptor agonist medicine, not the natural hormone.
Researchers are still studying other possible effects of GLP-1 signaling, from the heart to the kidneys, which is why some labels now list uses beyond blood sugar and weight.
Why it matters
Knowing what GLP-1 does explains both the appetite drop and the stomach side effects people notice on these medicines.
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