What Is “GLP-3”? Retatrutide’s Nicknames Decoded

Where the Name “GLP-3” Comes From

Semaglutide activates one receptor, GLP-1. Tirzepatide activates two, GIP and GLP-1. Retatrutide activates three: GIP, GLP-1 and glucagon.^[5][6][7] Counting receptors gives 1, 2, 3, and somewhere along the way the count was fused onto the GLP name. That produced "GLP-2" for dual agonists and "GLP-3" for triple agonists. The same counting produced "GLP-5" for retatrutide plus cagrilintide; see retatrutide and cagrilintide research.

Lilly’s own FAQ answers the question directly: "GLP-3" is a label "used informally in the media" for triple hormone receptor agonists, it does not represent "an actual scientific classification", and "triple agonist" is the accurate term.^[1]

The GLP-1/2/3 Numbering Myth

The numbers in GLP-1 and GLP-2 are not a ranking or a generation. Both are real hormones cut from the same precursor, proglucagon, and released together by L cells in the gut. GLP-1 is the incretin that the weight-loss drugs mimic. GLP-2 is a 33-amino-acid peptide that mainly acts on the intestine, where it promotes growth and absorption.^[2]

GLP-2 already has its own approved medicine. Teduglutide, a GLP-2 analogue sold as Gattex, was approved by FDA in December 2012 for short bowel syndrome.^[3] So when a seller lists tirzepatide as "GLP-2", the name points at the wrong hormone: tirzepatide does not act on the GLP-2 receptor at all.^[6] There is no hormone called GLP-3 and no GLP-3 receptor.

The Name Decoder

The labels below were collected from seller listings, forums and research databases and checked on October 10, 2026. Seller codes change often; a new prefix usually means a store has rebranded its listing, not that the molecule has changed. None of these codes is an official name, and a label alone tells you nothing about what is actually in a vial.

"Triple G" deserves a warning of its own. PubChem files the record with retatrutide’s molecular formula under the title "Triple G".^[8] Novo Nordisk uses the same phrase for UBT251, a different triple agonist of the GLP-1, GIP and glucagon receptors that it develops with United Biotechnology; a phase 2 trial in China reported up to 19.7% mean weight loss after 24 weeks.^[9] Blogs and sellers have started calling UBT251 a "GLP-3" too. Novo does not. Two different molecules can now sit behind the same nickname, which is one more reason to read the name of the compound, not the code.

Semaglutide vs Tirzepatide vs Retatrutide

Receptor targets and molecular weights are from KEGG DRUG; US approval dates are from Drugs@FDA.^{[5][6][7][10][11][12][13]} Lilly says retatrutide has not been approved by any regulatory agency and plans to submit a Biologics License Application to FDA in Q1 2027.^[14] For the full status by jurisdiction, see Is Retatrutide Approved?, and for the drug-versus-biologic question, Is Retatrutide a Peptide or a Biologic?

What TRIUMPH-1 Showed

TRIUMPH-1 is the pivotal phase 3 obesity trial. It randomized 2,339 adults with obesity and without diabetes to one of three retatrutide dose groups or placebo, once weekly for 80 weeks, and was published online in The New England Journal of Medicine on September 29, 2026.^[4]

Both columns are correct. The NEJM abstract reports the treatment-regimen estimand, which counts everyone randomized whether or not they stayed on treatment. Lilly’s May 21, 2026 topline release led with the efficacy estimand, which estimates the effect in people who kept taking the study drug, so its numbers are larger.^[4][15] The 25% and 28% figures circulating online are the same trial counted two ways.

The trial also enrolled two subgroups. In 574 participants with knee osteoarthritis, pain scores fell more than with placebo, and in 243 participants with obstructive sleep apnea, breathing events per hour fell more than with placebo (both P<0.001). The most common adverse events were gastrointestinal.^[4] The earlier phase 2 trial, also in NEJM, ran for 48 weeks.^[16] Reported adverse-event rates and the other phase 3 readouts are on the TRIUMPH trial tracker.

Is “GLP-3” Approved?

No. Lilly states that retatrutide is investigational, has not been approved by any regulatory agency, and is legally available only to participants in Lilly’s clinical trials.^[1] Lilly plans its US submission for Q1 2027.^[14]

A product labelled "GLP-3" is therefore never an approved medicine, whatever the code on the vial. Material sold by Remy Research is for laboratory research use only. For the UAE picture, see Retatrutide in the UAE.

How to Tell What’s in a Vial Labelled “GLP-3”

Because the label is a nickname, identity has to come from the lab, not the packaging. Three checks matter.

• Identity by mass (LC-MS). Retatrutide has the formula C221H342N46O68, an average molecular weight of 4,731.34 and a monoisotopic mass of 4,728.47.^[7][8] Tirzepatide (4,813.45) and semaglutide (4,113.58) are clearly different.^[6][5] A mass spectrometry result that matches retatrutide’s mass is the check that separates it from a relabelled tirzepatide or semaglutide vial.
• Purity by HPLC. An HPLC chromatogram shows how much of the material is the main peak. It does not by itself prove identity, which is why it is paired with LC-MS.
• A batch-matched COA. The certificate of analysis should carry the same batch or lot number as the vial, the tested mass, the purity and the date. A COA for a different batch tells you nothing about yours.

Our guide to verifying a third-party COA walks through each field, and our own reports are on the lab results page.

What This Page Does Not Cover

This is a naming guide. It does not give dosing, administration or handling instructions, and it makes no therapeutic or human-use claim. For the compound itself, see the retatrutide research profile, the reta peptide guide and the GLP-1, GIP and glucagon mechanism explainer. Listed mg per click for documented retatrutide pen formats is on the retatrutide pen clicks to mg page.