GLP-1 vs GLP-2 vs GLP-3
Direct answer
What you need to know
Evidence strength: StrongTwo of those are hormones. The third is not. GLP-1 and GLP-2 are both real, both cut from the same proglucagon gene, and both released by the same cells in your gut — but they do entirely different jobs, and GLP-2 has nothing to do with weight. There is no GLP-3 hormone. The term is informal shorthand people use for the next generation of investigational medicines, such as retatrutide, rather than a real peptide or an official drug class.
Key takeaways
- GLP-1 and GLP-2 come from the same gene and the same gut cells.
- GLP-2 acts on the intestinal lining; its analog treats short bowel syndrome, not obesity.
- No GLP-3 hormone exists — the proglucagon gene does not encode one.
- What people mean by “GLP-3” is usually an investigational multi-agonist that is not approved.
Important limitation: This page explains what each term refers to. It is not a comparison of treatments, because these are not alternatives to each other — they treat different conditions, and one of them is not a medicine at all.
Next action: If you arrived looking for a stronger weight-loss option than the current ones, the honest answer is that the larger numbers all belong to compounds you cannot be prescribed — the investigational ones are exactly that, and we flag their figures as pipeline data rather than approved results.
Primary sources: PubMed Central (PMC8312260), PubMed Central (PMC8171296), Research review, ResearchGate record
General education, not medical advice. Nothing here is a recommendation to seek out an investigational compound.
The two that are real
Both come from the same source. The proglucagon gene encodes glucagon, GLP-1 and GLP-2, and the enteroendocrine L-cells in your intestine release them in response to food arriving. Both are then broken down by the same enzyme, DPP-4 — which is why the medicines built from each of them share the same design problem, and the same solution.
| GLP-1 | GLP-2 | |
|---|---|---|
| Released by | Gut L-cells, when food arrives | The same L-cells, at the same time |
| What it does | Insulin release, slowed stomach emptying, reduced appetite | Acts on the intestinal lining — growth and barrier function |
| Medicines built from it | Semaglutide, tirzepatide, liraglutide, orforglipron | Teduglutide |
| What those treat | Type 2 diabetes, chronic weight management, sleep apnoea | Short bowel syndrome |
GLP-2 is not a rival to GLP-1 and not a weight-loss option. It is the same family of hormone doing a completely different job, and its medicine treats a condition most people reading this will never encounter.
The one that is not
There is no GLP-3. The proglucagon gene does not encode one, and no such hormone appears in the peptide family alongside glucagon, GLP-1 and GLP-2. If you have searched for it, you have not misunderstood something — you have encountered a term that circulates without a referent.
What people usually mean by it is the next generation: investigational compounds that act at more receptors than the current medicines do. Retatrutide is the one most often meant, and it acts at three.
Retatrutide is not an approved medicine
In TRIUMPH-1 it reported a 28.3% mean weight reduction — larger than anything an approved product has published. That figure is pipeline data. It is not FDA-approved, it cannot be prescribed, and anything sold to you under that name today is not a regulated medicine.
Calling that class “GLP-3” is understandable shorthand — it sounds like a version number — but it is worth resisting, because it implies an approved successor exists. It does not. The approved class is the one on our drug reference.
Why this distinction matters commercially
- A product marketed as a “GLP-3” is invoking a hormone that does not exist. That is a strong signal about the seller.
- Investigational compounds sold online are outside the regulated supply chain entirely — not approved, not reviewed for what they contain, and frequently labelled “research use only” while carrying dosing instructions.
- A trial result is not an approval. Impressive pipeline figures are the most effective material anyone selling an unapproved product has.
So which should you be asking about?
If the question is about weight or blood sugar, it is a GLP-1 question, and the useful comparisons are within that class rather than against GLP-2 — see GLP-1 vs semaglutide vs Ozempic for how the class, molecule and brand names fit together, or pill vs injection for the format decision.
Sources
Each source below supports specific statements on this page. We cite the strongest available authority and verify against the current version before publishing.
- Variation in the evolution and sequences of proglucagon and the receptors for proglucagon-derived peptides in mammalsPubMed Central (PMC8312260)Supports: That the mammalian proglucagon gene encodes glucagon, GLP-1 and GLP-2 — and that there is no GLP-3 among the proglucagon-derived peptides.
- Proglucagon-derived peptides as therapeuticsPubMed Central (PMC8171296)Supports: The wider proglucagon-derived peptide family, including oxyntomodulin and glicentin, and their therapeutic development.
- The discovery of GLP-2 and development of teduglutide for short bowel syndromeResearch review, ResearchGate recordSupports: GLP-2's intestinal role and teduglutide as the GLP-2 analog approved for short bowel syndrome.
- Diabetes, obesity and digestive-disease informationNational Institute of Diabetes and Digestive and Kidney Diseases (NIH)Supports: GLP-1 as an incretin hormone released by the gut after eating.
- StatPearls clinical referenceNCBI Bookshelf, U.S. National Library of MedicineSupports: Incretin physiology and the DPP-4 degradation shared by GLP-1 and GLP-2.
- Lilly's Triple Agonist Retatrutide Delivered Powerful Weight LossEli Lilly (investor release)Supports: The 28.3% weight reduction reported for retatrutide in TRIUMPH-1 · primary endpoint — investigational, and not FDA-approved.
This page is general education, not medical advice. Talk to your own healthcare provider about your situation before starting, stopping, or changing any medication.