Single, dual, triple. The three most-searched metabolic peptides differ by one simple thing — how many receptors they engage — and that difference shows up clearly in the trial data. Here's the 2026 head-to-head.
The entire class is easiest to understand by counting receptors engaged:
Each added receptor brings a distinct effect: GLP-1 drives satiety and insulin signaling, GIP supports glucose handling and adipose metabolism, and glucagon adds energy expenditure and lipolysis.
| Compound | Receptors | Peak trial weight loss* | Key program | 2026 status |
|---|---|---|---|---|
| Semaglutide | GLP-1 (single) | ~15% (68 wk) | STEP / SELECT | FDA-approved (Rx) |
| Tirzepatide | GLP-1 + GIP (dual) | ~21–23% (72 wk) | SURMOUNT | FDA-approved (Rx) |
| RetatrutideNewest | GLP-1 + GIP + glucagon (triple) | ~24–30% (48–104 wk) | TRIUMPH (Phase 3) | Investigational |
*Average reductions reported in their respective clinical programs at the doses and durations studied. Cross-trial comparisons are approximate — populations and protocols differ. Figures describe trial findings, not expected outcomes from research-grade material.
The trend is hard to miss: more receptors, more effect. Semaglutide established the category at roughly 15% average weight loss. Tirzepatide's dual mechanism pushed that into the low 20s. Retatrutide's triple mechanism produced the largest pharmacological weight reductions ever reported — around 24% at 48 weeks in Phase 2, and up to ~25–30% in the Phase 3 TRIUMPH program — with the glucagon arm widely credited for the extra effect through increased energy expenditure.
For the underlying retatrutide data, see our full retatrutide research page; for the class overview, see GLP-1 peptides explained.
A crucial distinction for 2026: semaglutide and tirzepatide are FDA-approved prescription medicines, while retatrutide is still investigational (Phase 3; projected decision late 2027–2028). On the compounding side, the GLP-1s are winding down as the national shortage resolves — we cover that in the 2026 FDA Peptide Regulation Update. The research-peptide market continues to sell all three strictly as research materials.
Because demand in this category is the highest in the entire peptide space, it's also where sourcing quality matters most. Buy only from vendors publishing batch-specific third-party COAs (HPLC + mass spec), with proper cold-chain or stable shipping and a verifiable reputation.
Our vetted picks for this category, with exact-product links:
Links are affiliate links, disclosed per FTC guidelines — you pay the same price and stay attributed to us while you browse. Compare every vendor on our peptide company comparison page.
Semaglutide proved the concept, tirzepatide raised the ceiling, and retatrutide — adding a third, thermogenic receptor — set the new high-water mark in trials. Two are approved medicines; one is still investigational. For research sourcing, the receptor count tells you the science, but the COA tells you whether what's in the vial matches the label.
Last reviewed June 2026. By the Peptides Uncaged Research Team.
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