Retatrutide Guide

What is actually known about retatrutide.

An independent reference to LY3437943, the triple GIP, GLP-1 and glucagon receptor agonist. Every figure below carries the tier of evidence behind it.

Status
Investigational, Phase 3
Approval
Not FDA approved
Last reviewed
July 2026

Reported weight reduction, by evidence tier

  • Peer-reviewed
  • Sponsor-reported
  • No data
  1. Weight reduction, 48 weeksPeer-reviewed

    24.2%

    Mean reduction in the 12 mg arm of the Phase 2 obesity trial, published in the New England Journal of Medicine.

  2. Weight reduction, 80 weeksSponsor-reported

    28.3%

    Upper figure in Lilly’s Phase 3 topline announcement. Company-reported and not yet peer-reviewed.

  3. Safety beyond trial durationNo data

    No data

    No published evidence exists for outcomes past the longest completed trial. The interval spans the axis because nothing constrains it.

Marker position is the figure as reported. Interval width indicates the tier of evidence supporting it, not a computed confidence interval. Trials differ in length, population and design, so the two figures above are not directly comparable.
Sourced to NEJM, The Lancet and ClinicalTrials.govNo sellers named, no affiliate links

The compound

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 that is still under study, and it is the reason retatrutide is not simply a stronger version of the drugs already on the market.

Neither the Phase 2 publication nor the Phase 3 topline announcement makes retatrutide an approved medicine. It cannot be prescribed as one, and material sold under a research label is not the trial compound.

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

Every major question, answered from the record

Each page separates peer-reviewed findings from company reports and from what nobody yet knows.

What Is Retatrutide?

Mechanism, development history and regulatory status.

Dosage Research

Verified dose arms and escalation methods used in trials.

Concentration Calculator

Educational units analysis with strict safety context.

Side Effects

Gastrointestinal events, heart-rate findings and unknowns.

Retatrutide vs Tirzepatide

A careful comparison with tirzepatide and semaglutide.

Researched Effects

Weight, glycemic, metabolic and liver-fat research.

Cost Factors

Why no approved price exists and what may shape one.

Trial Timelines

What before-and-after evidence means in research.

Access Status

Clinical trials, regulation and the 2026 access picture.

Prescribing Information

Why no FDA label exists and how to check any document.

Clinical Trials

How enrolment works, who qualifies and how to spot a fake offer.

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.

  • Every claim linked to primary research
  • Company-reported results labeled as such, until peer review
  • Cross-trial comparison limits kept visible
  • Pages reviewed and dated

Read the editorial approach