Published Aug 31, 2026 · Updated Aug 31, 2026
Is There a "GLP-3"? What People Actually Mean (Retatrutide, Explained)
"GLP-3" isn't a real drug or hormone — but the medication people mean is very real. Here's what retatrutide is, its Phase 3 results, and when it may arrive.
Short answer: there is no such thing as GLP-3. No hormone called GLP-3 plays a role in appetite, and no drug class by that name exists. But the medication people mean when they say "GLP-3" is very real, and it's the most closely watched drug in obesity medicine: retatrutide, Eli Lilly's triple-agonist now in late-stage trials.
The confusion is understandable — you'll even hear founders and clinicians say "GLP-3" on stage at health conferences (here's one at DLD Health, discussing the drug's 30% weight-loss results under that name).9 Here's what's actually going on.
Where "GLP-3" comes from
The naming logic feels intuitive: Ozempic and Wegovy (semaglutide) act on one gut-hormone receptor, GLP-1. Mounjaro and Zepbound (tirzepatide) act on two — GLP-1 plus GIP — and got nicknamed a "dual agonist." So a drug that acts on three receptors must be "GLP-3," right?
Not quite. Retatrutide targets three different hormone receptors: GLP-1, GIP, and glucagon.4 The "3" people reach for describes the number of pathways, not a third generation of the GLP hormone. The accurate name is a triple agonist (or "triple G"). There is a GLP-2, incidentally — it's involved in gut lining growth, not weight8 — which is part of why "GLP-3" makes endocrinologists wince.
What retatrutide actually is
Retatrutide is a once-weekly injectable developed by Eli Lilly. Adding glucagon receptor activity to the GLP-1/GIP combination does something the earlier drugs don't: alongside suppressing appetite, it appears to increase energy expenditure — pushing the body to burn more, not just eat less.4
The Phase 3 results everyone is talking about
In May 2026, Lilly published results from TRIUMPH-1, an 80-week, randomized, double-blind, placebo-controlled Phase 3 trial with 2,339 participants:2
At 80 weeks, average weight loss was 19.0% on 4 mg, 25.9% on 9 mg, and 28.3% on 12 mg (about 70 lb / 32 kg at the top dose).2 In a 104-week extension for participants with BMI ≥ 35, the 12 mg group reached 30.3% average weight loss.2 Perhaps most striking: 45.3% of participants on 12 mg lost 30% or more of their body weight — territory previously reserved for bariatric surgery — and 65.3% ended the trial with a BMI under 30.2
For context, semaglutide's landmark trials averaged ~15% weight loss and tirzepatide's ~21%.56 Retatrutide is a step change, and additional Phase 3 readouts (including two more successful obesity trials Lilly announced in 2026) are expected to complete the picture.1
The trade-offs
More receptors, more effect — and more side effects. Gastrointestinal issues dominated and rose with dose: nausea (29–42%), diarrhea (25–34%), constipation (24–26%), vomiting (11–25%).3 Discontinuation due to side effects climbed from 4.1% at 4 mg to 11.3% at 12 mg.3
And weight loss this fast raises the stakes on a problem that already exists with GLP-1s: a meaningful share of rapid weight loss comes from muscle and bone, not just fat, if the drug isn't paired with resistance training and adequate protein. Losing 30% of your body weight without protecting lean mass is not a health outcome — it's a different health problem. (We cover this in depth in our guide to muscle and bone loss on GLP-1s.)
When can you get it?
Retatrutide is not FDA-approved and not legally available as of August 2026. Lilly has not announced an approval date; remaining Phase 3 data is expected through 2026, putting a realistic approval window in 2027 if results hold.
One warning worth making explicit: because of the hype, gray-market "research peptide" sellers already offer products labeled retatrutide online. These are unregulated, unverified, and frequently counterfeit or misdosed.7 No legitimate source exists outside clinical trials today.
FAQ
Is GLP-3 a real hormone or drug? No. "GLP-3" is a colloquial (and incorrect) nickname for retatrutide, a triple agonist targeting GLP-1, GIP, and glucagon receptors.4
How much weight do people lose on retatrutide? In Phase 3 trials: 28.3% average at the highest dose over 80 weeks, rising to 30.3% at 104 weeks in the extension cohort.2
Is retatrutide stronger than Ozempic or Mounjaro? In trial data, yes — average weight loss is roughly double semaglutide's and clearly above tirzepatide's, with correspondingly higher GI side effect rates.2356
When will retatrutide be approved? No official date. With Phase 3 trials completing through 2026, 2027 is the earliest realistic window for FDA approval.
Can I buy retatrutide now? No legal, safe route exists. Anything sold online today as retatrutide is unregulated and potentially dangerous.7
This article is for information only and is not medical advice. Investigational drugs discussed here are not approved for use. Talk to a licensed clinician about approved treatment options.
- 1.Retatrutide delivered powerful weight loss in a pivotal Phase 3 obesity trialThe TRIUMPH-1 topline announcement, May 2026Eli Lilly and Company↩
- 2.Retatrutide achieves up to 30.3% average weight loss in Phase 3 TRIUMPH-1Trial design, dose-by-dose results and the 104-week extensionAJMC↩
- 3.Retatrutide delivers bariatric-level weight loss in pivotal Phase 3 TRIUMPH-1The adverse-event and discontinuation figures by dosePharmacy Times↩
- 4.Triple-hormone-receptor agonist retatrutide for obesity — a Phase 2 trialJastreboff et al., on the three receptors and energy expenditureNew England Journal of Medicine↩
- 5.Once-weekly semaglutide in adults with overweight or obesity (STEP 1)Wilding et al., the trial behind Wegovy's headline figureNew England Journal of Medicine↩
- 6.Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)Jastreboff et al., the trial behind Zepbound's headline figureNew England Journal of Medicine↩
- 7.FDA's concerns with unapproved GLP-1 drugs used for weight lossThe agency's standing warning on products sold outside the approved supply chainUS Food and Drug Administration↩
- 8.GLP-2 and the regulation of intestinal growth and functionBrubaker, on what the other glucagon-like peptide actually doesComprehensive Physiology↩
- 9.The new peptides story: how GLP-1s are changing mental healthA conference interview that uses the "GLP-3" nickname on stageDLD Health↩
NADAC figures are pharmacy acquisition costs, not retail prices and not what you will pay. This content is educational and is not medical advice.