GLP-1 Glossary: Every Term, Abbreviation and Brand Name Decoded

The GLP-1 space has accumulated a forest of terms — multiple drug names for the same molecule, several spellings of the same abbreviation, related-but-distinct drug classes, and a couple of search-engine typos that get used as if they're real terms. This glossary covers all of it.

The core terms

GLP-1 Glucagon-like peptide-1. A 30- or 31-amino-acid hormone naturally released by the small intestine after meals. Stimulates insulin release, suppresses glucagon, slows gastric emptying and suppresses appetite.

GLP-1 receptor The protein the GLP-1 hormone (and its drug mimics) bind to. Found on pancreatic beta cells, neurons in the brain, GI tract cells, heart and other tissues.

GLP-1 receptor agonist (GLP-1 RA) A drug that activates the GLP-1 receptor, mimicking the effects of the natural hormone. The full drug class. Examples: semaglutide, tirzepatide, liraglutide.

GLP-1 analog Synonym for GLP-1 receptor agonist when the drug is a peptide closely resembling the natural hormone (e.g., semaglutide). Some recent agents are small molecules rather than analogs — they're agonists but not analogs.

GLP-1 agonist Common shorthand for GLP-1 receptor agonist.

Search-engine variants of "GLP-1"

People type the term many ways. They all mean the same hormone / drug class:

• GLP1, GLP 1, GL P1, GL P 1, g lp 1 — variant spellings of GLP-1
• glp1s, GLP-1's — plural forms
• glp 1i, GLP1 i — typos for GLP-1 (or attempts to refer to "GLP-1 inhibitor", which isn't really a drug class)

If you searched for any of these, you're looking for GLP-1 receptor agonists — the drugs covered throughout this site.

Common mix-ups: "GLP-1 inhibitor"

"GLP-1 inhibitor" is not a real drug class. People searching this term usually mean one of two things:

1. GLP-1 receptor agonists (what GLP-1 drugs actually are)
2. SGLT2 inhibitors — a different diabetes drug class: empagliflozin (Jardiance), dapagliflozin (Farxiga), canagliflozin (Invokana)

See GLP-1 vs SGLT2 inhibitors.

Related hormones and classes

GIP Glucose-dependent insulinotropic polypeptide. A second incretin hormone, alongside GLP-1. Activated by tirzepatide and retatrutide.

GLP-2 A different peptide derived from the same proglucagon gene as GLP-1. Involved in gut growth and intestinal barrier function. Not a target of the current GLP-1 receptor agonists.

Glucagon The hormone that opposes insulin — raises blood sugar by prompting the liver to release stored glucose. Targeted (in combination with GLP-1 and GIP) by retatrutide for its energy-expenditure effects.

Amylin A pancreatic hormone that complements insulin, slowing gastric emptying and reducing appetite. Targeted by cagrilintide (the second molecule in Novo's upcoming CagriSema combination).

Incretin Category of hormones (GLP-1, GIP) released by the gut that increase insulin secretion in response to eating. The "incretin effect" is the finding that oral glucose triggers more insulin release than IV glucose.

DPP-4 Dipeptidyl peptidase-4. The enzyme that rapidly breaks down endogenous GLP-1 (giving it a 2-minute half-life). DPP-4 inhibitor drugs (sitagliptin / Januvia, etc.) work by blocking this enzyme to boost endogenous GLP-1.

DPP-4 inhibitor A different drug class that boosts endogenous GLP-1 by blocking the DPP-4 enzyme. Less potent than GLP-1 receptor agonists. Examples: sitagliptin (Januvia), linagliptin (Tradjenta).

Drug classes by mechanism

Drug names: generic → brand

Other key terms

STEP — Novo Nordisk's Phase 3 trial program for semaglutide in obesity (STEP-1 through STEP-4, STEP-TEEN, etc.).

SUSTAIN — Novo Nordisk's Phase 3 program for semaglutide in T2D.

SELECT — Novo's cardiovascular outcomes trial for semaglutide in patients with obesity and CVD. Showed 20% MACE reduction.

SURPASS — Eli Lilly's Phase 3 program for tirzepatide in T2D.

SURMOUNT — Eli Lilly's Phase 3 program for tirzepatide in obesity.

TRIUMPH — Eli Lilly's Phase 3 program for retatrutide.

OASIS — Novo's Phase 3 program for oral Wegovy.

ATTAIN — Lilly's Phase 3 program for orforglipron / Foundayo.

STEP-1 — The pivotal Wegovy trial showing 15% average weight loss at 68 weeks.

SURMOUNT-1 — The pivotal Zepbound trial showing 21% average weight loss at 72 weeks.

MACE — Major adverse cardiovascular events. Heart attack, stroke, cardiovascular death.

MASH — Metabolic-associated steatohepatitis. Liver disease driven by metabolic factors. Wegovy is approved for MASH with fibrosis.

NASH — Older name for MASH. Same disease; nomenclature updated.

MTC — Medullary thyroid carcinoma. The thyroid cancer signal from rodent studies that earned GLP-1s their boxed warning.

MEN-2 — Multiple endocrine neoplasia syndrome type 2. A genetic condition associated with MTC. Personal or family history is a contraindication for GLP-1s.

OSA — Obstructive sleep apnea. Zepbound is approved for moderate- to-severe OSA in adults with obesity.

T2D — Type 2 diabetes.

BMI — Body mass index.

FDA — US Food and Drug Administration.

503A pharmacy — A traditional US compounding pharmacy that prepares medications for individual patients with patient-specific prescriptions.

503B outsourcing facility — A larger-scale FDA-regulated compounding facility that can prepare batches for office use or during drug shortages.

LillyDirect — Eli Lilly's direct-to-consumer pharmacy program; sells Zepbound vials and Foundayo at reduced cash prices.

NovoCare Pharmacy — Novo Nordisk's direct-to-consumer pharmacy program; sells Wegovy and other Novo products at reduced cash prices.

Compounded GLP-1 — Same active molecule as brand-name (semaglutide or tirzepatide) but prepared by a US-licensed compounding pharmacy rather than the original manufacturer. See compounded GLP-1.

Research peptide — Vials sold as "for laboratory research only, not for human consumption." Not pharmaceutical products. Not a legal route for clinical use.

Microdosing — Informal term for staying at or below the lowest approved dose of a GLP-1. See GLP-1 microdosing.

Titration — The process of gradually increasing a drug dose from starter to target over several weeks. Standard for all GLP-1s.

Maintenance dose — The sustained dose after titration completes. For Wegovy this is 2.4 mg/week; for Zepbound, 5-15 mg/week.

Off-label use — Using a drug for an indication not on its FDA approval. Common with GLP-1s (e.g., using Ozempic for weight loss).

FAQ

What does GLP-1 stand for? Glucagon-Like Peptide-1.

What's the difference between GLP-1, GLP1 and GLP 1? Same thing. Different spellings/formats of the same abbreviation.

Is "GLP-1 agonist" the same as "GLP-1 receptor agonist"? Yes. The shorter form is colloquial.

Is "GLP-1 inhibitor" a real drug class? No. People searching that term usually mean GLP-1 receptor agonists or the unrelated SGLT2 inhibitors.

Are all the GLP-1 drug brands the same? No. Different brands have different molecules, indications, doses and prices. See GLP-1 drugs list.

This article is for educational purposes only and is not medical advice. GLP-1 medications are prescription drugs. Consult a qualified healthcare professional for treatment decisions.