GLP-3 RT is a vendor-coined label for retatrutide, the investigational GLP-1/GIP/GCGR triple-agonist peptide (CAS 2381089-83-2, 39 amino acids, C18 fatty-diacid acylation). The "RT" stands for retatrutide. Multiple vendors that sell "GLP-3 RT" list that exact CAS number and the retatrutide amino-acid sequence on their own product pages, so the rename is cosmetic, not chemical. Dose-size variants like "GLP-3 RT 20" or "RT-30" just denote a 20 mg or 30 mg vial. It is a research-grade compound — there is no FDA-approved retatrutide product under any name.
The short version
"GLP-3 RT" is retatrutide wearing a different sticker. It is not a new peptide, not a more advanced one, and not a distinct chemical entity. The vendors selling it tell you so themselves — on the same product page that uses the GLP-3 RT name, they print CAS 2381089-83-2, the registry number for retatrutide (Eli Lilly's LY3437943), alongside the drug's 39-amino-acid sequence. The label is marketing; the molecule is the Phase 3 triple agonist.
There is no such thing as a "GLP-3 receptor." Retatrutide is an agonist at three incretin receptors — GLP-1, GIP, and glucagon (GCGR) — and "GLP-3" is a vendor coinage gesturing at that triple action. The "RT" is retatrutide. Once you read it that way, every "GLP-3 RT" listing decodes cleanly.
How we know it's retatrutide
Three identifiers, all printed on vendor listings that carry the GLP-3 RT name:
- CAS 2381089-83-2. This is retatrutide's registry number. A CAS number is compound-specific; it does not change with a brand rename.
- The 39-amino-acid sequence beginning Tyr-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp… with a lysine bearing a C18 fatty-diacid side chain for albumin binding — the published retatrutide structure.
- Triple-receptor description (GLP-1 / GIP / glucagon). That mechanism is retatrutide's defining feature; no other marketed research peptide matches it.
When the vendor's own data sheet lists the CAS number and sequence of retatrutide, the rename is cosmetic by definition. You are not taking the vendor's word — you are reading their chemistry against the registry.
Why the relabel happens
We don't assign motive we can't evidence. What we can say: renaming a recognizable Phase 3 drug to a generic-sounding code has predictable effects. It lowers the listing's visibility against searches for the real compound, it slips keyword filters on payment processors and ad platforms, and it makes honest per-mg comparison between vendors harder. The same pattern shows up across the market — see /articles/code-name-catalogs-fda-evasion and our taxonomy of how to spot aliased peptide vendors.
Search demand for the term clusters tightly around specific brand names rather than any chemical nomenclature, which is the tell that "GLP-3 RT" is a brand-propagated label, not an industry one. A label that exists only on storefronts and not in any pharmacology reference is a label doing marketing work, not science.
GLP-3 RT vs tirzepatide (and "GLP-2 TRZ")
The same vendors that relabel retatrutide as "GLP-3 RT" often relabel tirzepatide as "GLP-2 TRZ" — a dual GLP-1/GIP agonist, two receptors instead of three. So the house naming maps cleanly:
- GLP-3 RT → retatrutide — triple agonist (GLP-1 + GIP + glucagon).
- GLP-2 TRZ → tirzepatide — dual agonist (GLP-1 + GIP).
If you're comparing the two as compounds rather than labels, the real distinction is the glucagon-receptor arm, which retatrutide adds and tirzepatide lacks. Our compound guides cover each: retatrutide and tirzepatide, with the head-to-head at retatrutide vs tirzepatide.
Reading the dose-size notation
The numbers appended to the label — "GLP-3 RT 20," "RT-30" — are vial sizes in milligrams, not doses. A "GLP-3 RT 20" is a 20 mg vial of lyophilized retatrutide; "RT-30" is 30 mg. Reconstitution and the trial-published dose levels are a separate question; the dosing schedules used in the TRIUMPH program are documented at /articles/retatrutide-dosing-protocols, and the reported side-effect profile at /articles/retatrutide-side-effects. We state vial size; we do not recommend a human dose.
How to verify before you buy
Treat any "GLP-3 RT" listing as unverified until it clears the same checks we'd apply to a listing labeled retatrutide:
- CAS on the listing reads 2381089-83-2.
- A per-batch COA exists and resolves in the lab's public index — paste it into /tools/coa-verifier.
- Mass-spec identity is on the COA, not just an HPLC purity percentage. Identity confirms it's retatrutide; purity only says how clean the sample is.
Vendors we've profiled that use the GLP-3 RT-style label include Research Peptide Hub (which sells it as "GLP-3 RT" with a Freedom Diagnostics COA). Vendors selling the same compound under its real name with independent Janoshik COAs include CertaPeptides. The naming choice itself is a data point about how a vendor treats transparency.
Where to buy retatrutide
If you've decoded "GLP-3 RT" back to retatrutide and want the observable market — current per-mg pricing, which vendors publish verifiable COAs, and the regulatory framing — that's maintained, auto-refreshed from vendor catalogs, at where to buy retatrutide in 2026. Compare on the real compound name, not the house label, and the per-mg picture gets a lot clearer.
Related
Frequently asked
Is GLP-3 RT the same as retatrutide?
Yes. "GLP-3 RT" is a house label, not a distinct molecule. Vendors selling it list CAS 2381089-83-2 — the registry number for retatrutide (Eli Lilly's LY3437943) — and the same 39-amino-acid sequence with the C18 fatty-diacid side chain. The "GLP-3" part is a marketing nod to it hitting three incretin receptors (GLP-1, GIP, glucagon); the "RT" is retatrutide. Chemically identical, different sticker.
What does GLP-3 RT stand for?
"GLP-3" is not a real receptor class — there is no GLP-3 receptor. It's a vendor shorthand implying a third-generation / triple-receptor incretin agonist (GLP-1 + GIP + glucagon). "RT" abbreviates retatrutide. The name is a branding device that obscures the compound's real identity, which is why it shows up on grey-market storefronts rather than in any pharmacology literature.
Why do vendors rename retatrutide to GLP-3 RT?
Renaming a recognizable Phase 3 drug to a generic-sounding code reduces its searchability against the real compound name, complicates payment-processor and platform keyword filters, and makes per-mg cross-vendor comparison harder for buyers. Whatever the motive, relabeling a headline compound is a transparency flag — verify the CAS number and the COA before treating "GLP-3 RT" as anything other than retatrutide.
What is the dosage notation on GLP-3 RT 20 / RT-30?
The trailing number is the vial size in milligrams — "GLP-3 RT 20" is a 20 mg vial, "RT-30" is 30 mg. It is not a dose. Trial dosing for retatrutide in the TRIUMPH program is published separately; see /articles/retatrutide-dosing-protocols. This article does not recommend any human dose.
How do I verify GLP-3 RT is actually retatrutide?
Check three things on the vendor's own listing. (1) CAS number — it should read 2381089-83-2. (2) The published per-batch COA — paste the URL into /tools/coa-verifier and confirm the lab (Janoshik, Liquilabs, etc.), batch ID, and date appear in the lab's public index. (3) Mass-spec identity on the COA, not just an HPLC purity figure — purity tells you how clean it is, identity tells you it's the right molecule. A "GLP-3 RT" listing with no CAS and no batch COA is unverified.
Is GLP-3 RT / retatrutide legal to buy?
Retatrutide is not a controlled substance, so federal possession is not criminalized in the US, but it is not FDA-approved for any use, so vendor sales are framed as research-use-only. Renaming it "GLP-3 RT" does not change that status. Internationally shipped vials carry customs-seizure risk. See /tools/peptide-legality for the per-compound status table.