Skip to content
PEPTIDESUNCENSORED

Retatrutide

/reh-tah-TROO-tide/aka LY3437943, Reta, Triple agonist

Once-weekly triple agonist (GLP-1, GIP and glucagon receptors) in late-stage trials for obesity.

SubcutaneousWeekly
Open in cycle visualizer

Retatrutide: educational research discussion. Not medical advice. Not a protocol for you.Details

Reported range
4–12 mg weekly
Frequency
Once weekly
Cycle length
Continuous, after stepwise titration
Half-life
≈ 6 days
Route
SC

Reported figures describe what is published or discussed. None of them is a dose for you.

Mechanism

What it is proposed to do

One peptide, three receptors. GLP-1 and GIP receptor activation reduces appetite, slows gastric emptying and boosts glucose-dependent insulin release. Glucagon receptor activation raises energy expenditure and drives fat oxidation in the liver. The glucagon arm is what separates it from tirzepatide and is the likely reason for its large effect on liver fat.

  1. 01

    Retatrutide

    Once-weekly SC peptide, ~6-day half-life

    established
  2. 02

    GLP-1 + GIP receptors

    Appetite down, insulin release up, slower gastric emptying

    established
  3. 03

    Glucagon receptor

    Energy expenditure up, liver fat oxidation up

    established
  4. 04

    Weight and liver-fat loss

    Shown in Phase 2 and Phase 3 RCTs

    established
EstablishedProposed from animal or cell data

Half-life. About 6 days, which supports once-weekly dosing.

Dosing & cycles

What is reported, and where it comes from

Numbers below are labeled FDA label, clinical trial range or commonly reported range. They describe the published and discussed landscape. They are not instructions and not a protocol for you.

Dosing studio

Every figure is labeled by where it comes from.

This is not your dose

Scale view: Phase 3 maintenance doses (TRIUMPH-1)

0
5
10
15
20

Probe at 8 mg: inside the reported band (4–12 mg). Drag it to read the scale. It does not pick a number for you.

Typical cycle, as a calendar

Trial-style weekly titration

Escalate over months, then continuous

The conceptual shape of trial escalation: start low, step up at fixed intervals toward a maintenance dose, then continue weekly. Exact steps belong to the trial protocol.

OffLow / startMid / loadingHigh / maintenance

Cycle patterns

Trial-style weekly titration

Escalate over months, then continuous

The conceptual shape of trial escalation: start low, step up at fixed intervals toward a maintenance dose, then continue weekly. Exact steps belong to the trial protocol.

Start low
Step up
Step up
Step up
Maintenance
Week 1Week 24

Stacks

What it gets combined with

Why people pair things, and what nobody has tested.

GLP + anything

3 compounds
RetatrutideBPC-157Ipamorelin
Why people combine these
People add repair or GH-axis peptides hoping to offset GI side effects or protect lean mass.
Caution
Retatrutide already moves heart rate, GI function and glucose. Adding unverified compounds makes it impossible to tell what caused what, and no interaction data exist.
What is unknown
No published human data on this combination: dosing, interactions and long-term effects are all unstudied.

Evidence

How much of this is known

Evidence grade

A

Strong human evidence

Multiple adequate human RCTs and/or FDA approval for a defined indication.

How we grade

Graded A for weight-loss efficacy on the strength of large randomized trials. Not approved, and long-term safety is still being characterized.

Human trial status

Phase 2 (NEJM 2023): up to 24.2% mean weight loss at 48 weeks on 12 mg. Phase 3 TRIUMPH-1 topline (May 2026, 2,339 adults): 19.0%, 25.9% and 28.3% mean weight loss at 80 weeks on 4, 9 and 12 mg, and 30.3% at 104 weeks in a prespecified extension cohort on 12 mg. More Phase 3 readouts are expected. No approval has been announced.

Limitations

  • Phase 3 numbers are company topline results until full peer-reviewed publication.
  • Safety beyond about two years of treatment is unknown.
  • Weight regain after stopping is expected from the GLP-1 class but not yet characterized for retatrutide.

Sources to read

Links open PubMed, DailyMed, FDA or trial-registry searches. We do not cite what we have not described accurately.

Safety

Side effects, cautions, status

Commonly reported effects

  • GI effects dominate. In TRIUMPH-1 at 12 mg: nausea 42%, diarrhea 32%, constipation 26%, vomiting 25% (placebo: 15%, 14%, 11%, 5%).
  • Dose-dependent heart-rate increases were seen in Phase 2.
  • Dysesthesia (altered skin sensation) was reported, mostly mild to moderate.
  • Discontinuation rose with dose: 11.3% at 12 mg vs 4.9% on placebo in TRIUMPH-1.
  • Rapid weight loss carries its own risks: gallstones, lean-mass loss, dehydration from GI losses.
NauseaGI upsetAppetite suppressionHeart rate increaseNumbness / tingling

Who should be extra cautious

  • Medullary thyroid cancer or MEN2 history. GLP-1 class labels carry this contraindication. Expect the same caution here.
  • Pregnancy or planning one. Not studied. GLP-1 class labels advise stopping ahead of a planned pregnancy.
  • Pancreatitis or gallbladder disease. Class-wide caution for incretin drugs.
  • Gray-market "reta". Not the Lilly product. Identity, dose and sterility are unverified.
  • Tested athletes. Unapproved drug, prohibited under WADA S0.

Legal & regulatory status

Investigational. Not approved by the FDA or any other regulator as of September 2026. Anything sold online as "retatrutide" is not the Lilly trial product.

WADA. Not named individually, but drugs still in clinical development fall under S0 (non-approved substances).

Storage & handling, high level

Trial product is supplied by the sponsor under controlled conditions. Research-market vials are powder of unverified identity. Nothing on this page makes those equivalent.

Reconstitution and injection technique are clinical skills. The reconstitution calculator does arithmetic only.

FAQ

Questions people ask about Retatrutide

Is retatrutide FDA-approved?
No. As of September 2026 it is investigational. Phase 3 trials have reported topline results and an approval decision has not been announced.
Why do people call it GLP-3?
Internet shorthand for a third-generation GLP drug. There is no GLP-3 hormone.
How is it different from tirzepatide?
Tirzepatide targets GLP-1 and GIP. Retatrutide adds the glucagon receptor, which raises energy expenditure and burns liver fat. The trade-off at the top dose appears to be more GI effects and some heart-rate increase.
What about research-market retatrutide?
It is not the trial drug. Nobody outside Lilly's supply chain can guarantee identity, dose or sterility, and trial results do not transfer to an unverified vial.

The monthly Evidence Brief

Keep up with the evidence

One email a month: new trials, grade changes and FDA or WADA updates across the whole atlas, Retatrutide included. You get the free guide right away.

Cover of the free guide, 10 Peptide Claims, Fact-Checked

Free guide · PDF

10 Peptide Claims, Fact-Checked

13 pages · sent to your inbox right away

Email only. Unsubscribe from any email in one click. We do not sell or rent your address. Nothing we send is medical advice. Privacy