Retatrutide is the most-watched investigational peptide in metabolic research right now. Search interest jumped roughly 8x in 12 months, the Phase 2 results published in the New England Journal of Medicine reported the largest weight-loss percentage ever recorded for a pharmacologic agent in trials, and the Phase 3 TRIUMPH program is currently enrolling thousands of participants across multiple indications. This is a plain-English research guide to what it is, how it works, and where the evidence actually sits.
RUO framing throughout. New-U supplies retatrutide strictly as a laboratory reagent under our GLP-1 RC-R SKU. It is investigational, not approved by FDA / EMA / MHRA, and not for human consumption or weight-loss application. Clinical-trial outcomes do not transfer outside the trial context.
Retatrutide (development code LY3437943, by Eli Lilly) is a synthetic peptide that simultaneously activates three metabolic receptors in a single molecule: GLP-1, GIP, and the glucagon receptor. That triple-agonist mechanism is what separates it from every approved drug in the category.
| Compound | Receptor targets | Approval status | Trial weight-loss % |
|---|---|---|---|
| Semaglutide (Ozempic, Wegovy) | GLP-1 only | FDA approved (2017 T2D; 2021 obesity) | ~15% at 68 weeks (STEP-1) |
| Tirzepatide (Mounjaro, Zepbound) | GLP-1 + GIP (dual) | FDA approved (2022 T2D; 2023 obesity) | ~22.5% at 72 weeks (SURMOUNT-1, 15mg) |
| Retatrutide | GLP-1 + GIP + Glucagon (triple) | Investigational, Phase 3 ongoing | ~24.2% at 48 weeks (Phase 2, 12mg) |
The retatrutide Phase 2 number (24.2%, Jastreboff et al., NEJM 2023) is striking partly because it was achieved in 48 weeks, faster than the comparable semaglutide and tirzepatide endpoints (68 and 72 weeks respectively). Phase 3 outcomes are pending; clinical-trial evidence does not establish what would happen outside the trial protocol.
The molecule is engineered to bind and activate three receptors at once. Each contributes to the overall metabolic effect:
The hypothesis is that the third receptor closes the loop on energy balance: GLP-1 + GIP reduce intake, glucagon raises expenditure. The Phase 2 data is consistent with that hypothesis. Phase 3 evidence will test whether the effect holds at scale.
Retatrutide is being tested across multiple indications in the TRIUMPH Phase 3 program. The registered trials cover:
For the full breakdown of the Phase 3 evidence base and what each trial is measuring, see our companion piece on the retatrutide Phase 3 TRIUMPH program.
Semrush US-Google data through May 2026 shows search volume for "what is retatrutide" up roughly 8x over the prior 12 months. The fastest-rising related queries:
| Query | Vol/mo (US) | 12-month trend |
|---|---|---|
| what is retatrutide | 5,400 | +750% (0.12 to 1.00) |
| how long will 10mg of retatrutide last | 2,900 | rising |
| is retatrutide safe | 1,900 | rising |
| where to buy retatrutide | 1,900 | rising |
| how to get retatrutide | 1,600 | rising |
| how to reconstitute retatrutide | 1,300 | rising |
| is retatrutide FDA approved | 1,000 | rising |
For why so much of that demand is being captured by research-compound channels rather than clinical trial enrolment, see our piece on retatrutide online sourcing trends.
The primary Phase 2 publication (Jastreboff AM et al., Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial, NEJM, August 2023) ran 338 adults with obesity over 48 weeks. Reported outcomes at the highest 12mg dose:
Reported adverse events were predominantly gastrointestinal (nausea, diarrhoea, vomiting) and dose-dependent, consistent with the broader GLP-1 class. For the full outcomes breakdown including dose-response curves and how the numbers compare to semaglutide and tirzepatide Phase 3 endpoints, see retatrutide weight-loss percentage results.
Investigational status. Retatrutide is not approved by the FDA, EMA, MHRA, or any other major medicines regulator as of 2026. Phase 3 (TRIUMPH) is ongoing. Any retatrutide outside an active clinical trial is supplied as a research-grade reagent only and is not licensed for human consumption, weight-loss application, or any therapeutic purpose. It is also on the WADA Prohibited List (S2) and banned in any sanctioned competition.
What is retatrutide?
Retatrutide (development code LY3437943) is a synthetic peptide developed by Eli Lilly. It is a triple agonist - a single molecule that activates the GLP-1, GIP and glucagon receptors at once. Phase 2 results (NEJM, 2023) reported mean weight loss of around 24% at 48 weeks in the highest-dose arm, the largest figure published for any pharmacologic agent in trials to date.
Is retatrutide FDA approved?
No. As of 2026 retatrutide is investigational, currently in the Phase 3 TRIUMPH program with multiple registered trials on ClinicalTrials.gov. It is not approved by the FDA, EMA, MHRA or any other major regulator.
How does retatrutide work?
It activates three metabolic receptors simultaneously: GLP-1 (slows gastric emptying and central appetite), GIP (supports insulin secretion and adipose handling), and glucagon (increases energy expenditure - a mechanism the GLP-1-only and dual-agonist classes don’t engage). The triple mechanism is the basis for the unusually large weight-loss effect seen in trials.
How does retatrutide compare to semaglutide and tirzepatide?
Semaglutide (Ozempic, Wegovy) is single-receptor GLP-1. Tirzepatide (Mounjaro, Zepbound) is dual GLP-1/GIP. Retatrutide adds the third glucagon receptor on top, which explains the higher reported weight-loss percentages. Head-to-head trials are limited, so cross-trial comparison is not equivalent to a randomised comparison.
Where can I buy retatrutide for research?
Because retatrutide is unlicensed, no pharmacy or clinic can sell it - laboratories source it from research-compound suppliers that publish a per-batch CoA and label material research use only. New-U catalogues research-grade retatrutide as GLP-1 RC-R: sealed 10-vial packs verified to >99% HPLC purity by Janoshik and Freedom Diagnostics, tracked worldwide. Research use only.
How much does research retatrutide cost?
It is priced per vial in USD and scales by mg per vial from 5 mg up to 60 mg, so the per-mg cost drops on larger vials. Every tier ships in sealed 10-vial packs at >99% HPLC purity with a per-batch CoA; free shipping over $300, card and crypto accepted. See the GLP-1 RC-R (retatrutide) product page for current per-vial pricing.
Sealed vials of research-grade retatrutide, independently HPLC-verified at >99% purity by Janoshik and Freedom Diagnostics. Research use only - not for human consumption. Investigational compound, WADA-prohibited in sanctioned competition.
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