Drug facts

Retatrutide vs semaglutide

By David Chen·Editor·Reviewed August 2026

The difference that matters most³

It is not the receptor count. It is that one of these has a label — a document stating the dose, the storage, the interactions, the contraindications and every reaction rate — and the other has nothing of the kind, because it has not completed the process that produces one.

One receptor against three¹

Semaglutide is a GLP-1 receptor agonist: one receptor. Retatrutide acts on GIP, GLP-1 and glucagon receptors. More targets is a plausible reason to expect more effect, and it is equally a reason to expect more ways to go wrong — which is what trials are for.

What the retatrutide trials measured¹

The phase 2 obesity trial ran 48 weeks in adults with obesity and reported large mean weight reductions at the higher doses. A phase 3 trial in type 2 diabetes has since been published. Those are real results in real trials — and phase 2 is where a drug’s effect is estimated, not where it is confirmed.

Why you cannot compare the two numbers¹

Setting retatrutide’s phase 2 figure beside STEP 1’s −14.9% compares two different trials — different durations, different populations, different entry criteria, different phases of development. The only comparison that is not this mistake is a randomised head-to-head, and none has been published.

That is the same reasoning behind the semaglutide and tirzepatide page, where a head-to-head does exist.

What is being sold online³

Retatrutide is not an approved drug, so it cannot be lawfully compounded from an approved product the way this market compounds semaglutide. What is sold under the name is generally research-use material outside the pharmacy system entirely, with no prescriber, no pharmacy license and no accountable supply chain.

This index does not list it, and the four checks is the page on what a legitimate route actually looks like.