The Retatrutide Guide
Investigational peptide · Triple agonist

Retatrutide: The Complete Research Guide

Retatrutide (LY3437943) is an investigational peptide and triple GIP, GLP-1 and glucagon receptor agonist studied for weight and metabolic outcomes. This guide separates peer-reviewed evidence, new Phase 3 reports and unanswered questions.

Last reviewed: July 2026Evidence gradedFully referenced
At a glance

Quick facts

The key identifiers and research context in one place.

Compound
Retatrutide
Development code
LY3437943
Developer
Eli Lilly and Company
Class
GIP / GLP-1 / glucagon receptor agonist
Administration in trials
Subcutaneous, once weekly
Regulatory status
Phase 3; not FDA approved
Studied for
Obesity, type 2 diabetes and metabolic conditions
The compound

What is retatrutide?

Retatrutide is one molecule engineered to activate three hormone receptors. GLP-1 and GIP signaling overlap with existing incretin medicines; glucagon receptor activity adds a distinct metabolic pathway under study.

In 2023, a Phase 2 obesity trial reported an average 24.2% weight reduction at 48 weeks in the highest-dose group. In 2026, Lilly reported up to 28.3% at 80 weeks in Phase 3 topline results. Neither finding makes retatrutide an approved medicine.

Read the full explainer →
24.2%Average reduction at 48 weeks
12 mg · Phase 2
3Receptor targets
GIP · GLP-1 · glucagon
Phase 3Current development stage
Not FDA approved
Explore the evidence

A focused guide to every major question

Each article distinguishes peer-reviewed findings, trial design and current regulatory facts.

01

What is retatrutide?

Mechanism, development history and regulatory status.

02

Dosage research

Verified dose arms and escalation methods used in trials.

03

Concentration calculator

Educational units analysis with strict safety context.

04

Side effects

Gastrointestinal events, heart-rate findings and unknowns.

05

vs tirzepatide

A careful comparison with tirzepatide and semaglutide.

06

Researched effects

Weight, glycemic, metabolic and liver-fat research.

07

Cost factors

Why no approved price exists and what may shape one.

08

Trial timelines

What before-and-after evidence means in research.

09

Access status

Clinical trials, regulation and the 2026 access picture.

Editorial standard

Evidence first. Uncertainty included.

The Retatrutide Guide is an independent educational resource. It is not affiliated with Eli Lilly, is not a vendor and does not recommend unapproved products.

  • Claims linked to primary research
  • Company-reported results clearly labeled
  • Cross-trial limits kept visible
  • Pages reviewed and dated
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