Retatrutide vs Tirzepatide

The difference in one line

Tirzepatide acts at two receptors; retatrutide acts at three. Tirzepatide is a dual agonist at the GIP and GLP-1 receptors. Retatrutide is described in the published literature as a triple agonist, adding glucagon receptor activity to those two. Everything else that separates them follows from how much research each has behind it, not from the receptor count.

Side by side

The format and size grid is deliberately the same for both, so the choice between them is not forced by what happens to be in stock.

What the published research covers

This is the real asymmetry, and it runs the opposite way to the receptor count.

Tirzepatide has been through the full programme required of a licensed medicine. The reference trial is SURMOUNT-1, a phase 3 randomised double-blind placebo-controlled study run across 119 sites in nine countries, published in the New England Journal of Medicine (doi:10.1056/NEJMoa2206038). A later phase 3b trial, SURMOUNT-5, compared it head to head against semaglutide (doi:10.1056/NEJMoa2416394) — see tirzepatide vs semaglutide for what that trial was and what it reported.

Retatrutide's published human record is at phase 2: a randomised double-blind placebo-controlled trial reported in the same journal (PMID 37366315), alongside a phase 2a trial in metabolic dysfunction-associated steatotic liver disease and a structural-biology paper describing how the triple agonism at GLP-1R, GIPR and GCGR is achieved at the receptors themselves.

So: more receptors, less published human data. Those two facts sit together and neither cancels the other.

Why a higher receptor count is not a ranking

One receptor, two, three — it reads like a ladder, and it is not one. The receptor count describes what a molecule binds to. On its own it says nothing about the size of an effect, how well a compound is tolerated, or how much evidence exists behind it. Those are three separate questions and each is answered by a separate study.

Anyone presenting the count as a performance claim is describing chemistry and implying a result the chemistry does not contain. We are not going to do that, and the comparison above is the reason: the compound with fewer targets is the one with the completed trial programme.

Both are unlicensed research materials here

This needs saying flatly because it is where the comparison is most often got wrong. Tirzepatide holds a UK marketing authorisation as a licensed finished medicine, under its brand names. That authorisation belongs to that product, made to that specification, in that presentation, supplied through that route. It does not travel with the molecule.

What we supply is tirzepatide as an unlicensed research compound, on the same footing as everything else in the catalogue, with an analytical specification rather than a Summary of Product Characteristics. For the full version of that distinction, read retatrutide vs Mounjaro, which is the same comparison framed against the licensed product, and are peptides legal in the UK.

Formats, and what actually changes

Both are stocked as lyophilised vials and as pens. A vial holds freeze-dried powder and is reconstituted with bacteriostatic water; the reconstitution calculator covers the arithmetic, and how to reconstitute peptides covers the handling. A pen arrives already in solution.

The format changes the handling and nothing else. It does not change the compound, its specification or its status. If you want the vial route with the consumables included, both have a starter kit — retatrutide and tirzepatide — and peptide supplies lists the parts separately.

Supply note. Peptiq supplies research compounds for laboratory research use only. We are not a pharmacy and we do not supply licensed medicines. Where a licensed medicine is named on this page it is named to draw a distinction, not because we sell it, and nothing here is guidance on use.