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Being studied in people · not FDA-approved

Retatrutide

Also called Reta or Reta peptide.

Retatrutide is an experimental weekly injection being tested for weight loss. It acts on three hormone signals linked to appetite and metabolism.

What matters first

Why people look it up
People buy unapproved versions under the nickname Reta in hopes of losing weight.
What the evidence shows
A published phase 2 trial found large average weight loss. Phase 3 trials are underway, but FDA has not approved retatrutide.
Dose status
Trials tested Retatrutide at 1–12 mg once a week. There is no FDA-approved dose or dosing label. Every number below is a trial arm, not a treatment schedule.

Evidence snapshot

Published human trial

The fastest way to see what kind of evidence this page is built on.

Regulation
Not FDA-approvedNo US prescribing label
Dose source
Human trial regimens6 regimens · not a schedule
Safety evidence
6 listed safety findingsCommon and serious effects shown apart
Sources
7 cited sourcesMedical review complete · 2026-08-16
Open the shareable evidence image
Retatrutide at a glance: published human trial, dosing basis, regulatory status, safety coverage, and cited-source count. These details summarize the available sources; they are not treatment recommendations.

Further down: research and dosing details · results timeline · how it works · how good the evidence is · questions

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-08-16open the primary sources

What is known about Retatrutide

Retatrutide is a drug in late-stage weight-loss trials. It acts on three hormone pathways: GIP, GLP-1 and glucagon. The FDA has not approved it, so there is no official dose. In a published 48-week trial, researchers tested 1, 4, 8 and 12 mg once a week. Lilly has since announced early results from several phase 3 trials.

Retatrutide research and regulatory details: evidence quality, approval status, doses, handling, and presentation.
TopicValue
Strongest sourceHuman trial
FDA approvalNot FDA-approved
Studied dosing1–12 mg once weekly — from clinical trials
Typical vials10 mg · 20 mg · 30 mg

Every row links back to a source listed below. These facts are for reference, not a personal recommendation.

Weight-loss results over time

Retatrutide: Average weight loss at each study check-in

The studies checked weight after 24, 48 and 80 weeks. Results are group averages, not a forecast for one person.

  1. Phase 2 check-in

    24 weeks

    7.2%–17.5%

    People in the tested dose groups lost an average of this much weight. The placebo group lost 1.6%.

    Peer-reviewed · 338 participants in the full 48-week trial

  2. Phase 2 final result

    48 weeks

    8.7%–24.2%

    People in the tested dose groups lost an average of this much weight. The placebo group lost 2.1%.

    Peer-reviewed · 338 participants · same phase 2 trial

  3. TRIUMPH-1 phase 3 trial result

    80 weeks

    19.0%–28.3%

    People in the tested dose groups lost an average of this much weight. The placebo group lost 2.2%.

    Company announcement · 2,339 participants · NCT05929066

What these numbers mean

When each study checked weight and the average loss across the doses tested.

What they cannot tell you

They cannot tell you when one person will notice a change. The 80-week result came from a separate trial with different people.

TRIUMPH-1 phase 3 trial comes from a company announcement. A peer-reviewed paper is not available yet. The earlier 24- and 48-week results came from a published phase 2 study.

How Retatrutide works

Retatrutide acts at GIP + GLP-1 + glucagon. Here is what that means.

A triple agonist adds glucagon to the two gut-hormone signals. Glucagon is usually described as insulin’s opposite — the hormone that raises blood sugar when fuel runs low — so putting it in a weight-loss drug looks like a mistake until you separate its two jobs. Raising blood sugar is one. Raising how much energy you burn is the other, and the second one is the point.

◆ Receptor targets3 of 4 · GIP + GLP-1 + glucagon
4What each receptor does — 4 rows in the data table
Receptors targeted by Retatrutide, and what each receptor does
ReceptorRetatrutideWhat it does
GLP-1targetedLess appetite, slower stomach emptying, and insulin while blood sugar is rising. This is the intake side of the equation, and it is also what offsets what the glucagon arm does to blood sugar.
GIPtargetedThe second gut-hormone signal: more insulin while sugar is rising, plus effects on fat tissue and on appetite circuits that are still being argued about.
Glucagontargetedliver and adipose tissueRaises how much energy you burn, and pushes the liver to break down and burn fat. Where the gut-hormone arms cut what comes in, this arm raises what goes out — and pulls fat out of the liver while doing it.
Amylinnot targeted—

The same four receptor groups are shown for every drug, so the differences are easy to compare. Targets come from the drug class. Any result specific to Retatrutide comes from the cited sources.

Glucagon also makes the liver release glucose. The GLP-1 arm must therefore hold blood sugar steady while the glucagon arm works. A third pathway can add both power and new limits, including effects on heart rate and liver sugar. That balance is why these drugs are still being tested at several doses instead of prescribed.

What the evidence for Retatrutide is

These numbers come from a study in people that was published in a peer-reviewed journal. The drug or dose may still be experimental and may not have FDA approval.

Human trial

The trial behind the numbers

48-week phase 2 dose-finding trial · 338 participants · 48 weeks

Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med 2023;389:514-26 (PMID 37366315) · retrieved 2026-08-12

What it establishes
The study gave known doses to a defined group, monitored what happened and compared the results with another group.
What it does not establish
One trial cannot prove long-term safety or show that the result applies to everyone. The highest dose tested is a study dose, not a target for personal use.

Read each result with the study length, dose and number of participants. Results from separate trials are not a direct comparison because the people and study designs differ.

What each dose produced in the trial

These are the doses the trial gave and the weight change it reported for each one. It is a record of one experiment, not a schedule — no regulator has reviewed any of these doses.

◆ 48-week phase 2 dose-finding trial338 participants · 48 weeks

Average weight change from the start of the trial, by weekly dose · the dashed rule marks placebo

5Exact trial values — 5 rows in the data table
Retatrutide — 48-week phase 2 dose-finding trial: average weight change from the start for each dose group
Once-weekly doseStudy groupAverage weight changeWhat the paper notes
1 mgActive−8.7%1 mg group
4 mgActive−17.1%combined result for the two 4 mg groups
8 mgActive−22.8%combined result for the two 8 mg groups
12 mgActive−24.2%12 mg group
PlaceboControl−2.1%The group used to compare every active dose

What the source does not report for each dose group

At 48 weeks, the groups lost 8.7% of their starting weight at 1 mg and 24.2% at 12 mg, on average. The 4 mg and 8 mg groups lost 17.1% and 22.8%. The placebo group lost 2.1%.

Source: Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med 2023;389:514-26 (PMID 37366315) · retrieved 2026-08-12 · every value is quoted from that paper. Trial results describe averages across a study population, not an individual outcome.

Some bars are missing on purpose. Where the paper gives a range across arms instead of a figure per arm, that arm is left unplotted rather than filled in with a guess. The dashed line marks the placebo arm, so the part of each bar past it is the part the trial puts down to the drug rather than to being in a study.

How the trial reached those doses, step by step →

Where Retatrutide is in clinical trials

32 registered studies; the program has reached phase 3, and one is still enrolling.

The soonest a running study expects to finish measuring people is August 2026. That is when the sponsor expects to finish collecting the main measurement. It is not a results date, and not a date anything goes on sale.

  • Phase 3Recruiting

    A Master Protocol of Multiple Agents in Adults With Metabolic Dysfunction-Associated Steatotic Liver Disease (SYNERGY-Outcomes)

    Eli Lilly and Company · Metabolic Dysfunction-Associated Steatotic Liver Disease · 4,500 participants planned · started October 2025

    Main measurement due August 2030 (sponsor estimate)

    NCT07165028 on ClinicalTrials.gov

  • Phase 3Running, closed to new participants

    A Study of Retatrutide (LY3437943) in Participants Without Type 2 Diabetes Who Have Obesity or Overweight

    Eli Lilly and Company · Obesity, Overweight · 600 participants planned · started January 2026

    Main measurement due October 2028 (sponsor estimate)

    NCT07357415 on ClinicalTrials.gov

  • Phase 3Running, closed to new participants

    A Study of Retatrutide (LY3437943) in Participants With Obesity or Overweight

    Eli Lilly and Company · Obesity, Overweight · 250 participants planned · started November 2025

    Main measurement due July 2027 (sponsor estimate)

    NCT07232719 on ClinicalTrials.gov

We left one registration out of the count above. Registering a study does not prove it is running, and these did not hold up.

  • NCT07467447 — template batch: 7 of 8 studies from “Hudson Biotech” claim the same primary completion date 2027-02-14, all at Peking University Shenzhen Hospital; NCT07481734 declares itself an example

Check them yourself and disagree with us if you think we got it wrong.

A registered study means a sponsor filed a plan and started enrolling. It is not evidence the drug works, and most drugs tested in people never reach a pharmacy. Sponsors write and update these sources themselves; the National Library of Medicine publishes them without checking them.

ClinicalTrials.gov · retrieved 2026-08-23

Every compound we track, and what stage each one has reached →

Regulatory status

FDA has not approved retatrutide.

It is still in trials and has no dosing label. Any product sold today is unapproved. The doses here describe study groups, not advice.

Full regulatory tracker →

How Retatrutide compares

Each page says which kind of comparison it is: one trial that tested both, or two separate trials read side by side — which is much weaker, however close the numbers look.

The retatrutide half of retatrutide vs tirzepatide

Each page in retatrutide vs tirzepatide on its own terms, rather than folded into retatrutide.

Where to go next on Retatrutide

The schedule, the side effects and the mixing math each have their own page.

How the retatrutide trials escalated to their top arm

The strongest dose source for retatrutide is a published human trial.

The retatrutide reactions reported most often

Frequency bands exactly as the retatrutide source states them, with grouped figures kept grouped.

Convert a retatrutide amount to units on a U-100 barrel

Every step of the retatrutide arithmetic is printed, so the result can be checked by hand.

The 10 mg retatrutide vial: concentrations and example draws

A 10 mg retatrutide vial and a differently sized one are genuinely different arithmetic.

What each water volume does to the 20 mg retatrutide vial

Every option for the 20 mg retatrutide vial, with an example draw on a U-100 barrel.

Every published price for retatrutide, and its conditions

2 routes, walked in the order a reader meets them, with retatrutide as one example

Retatrutide and Australia’s Peptide products pathway

Retatrutide beside it — 6 personal-import conditions are published as a checklist rather than a blanket permission.

The 30 mg retatrutide vial: concentrations and example draws

A 30 mg retatrutide vial and a differently sized one are genuinely different arithmetic.

The official Canada Peptide products page beyond retatrutide

Retatrutide beside it — a “research use only” label does not legalize an unauthorized peptide drug.

Who else is sold for weight loss besides retatrutide

What people take it for and what the weight loss page shows stay in separate columns, including retatrutide

Safety notes

  • Investigational compound — no approved dosing exists
  • Trial doses are study information, not a recommendation

Questions about Retatrutide

Is Retatrutide FDA-approved?

No. There is no prescribing label for it, so no approved dose exists — the regulatory status section above has the detail.

How is Retatrutide taken?

By injection under the skin, once a week. The dosing page has every step, with the source on each row.

How does Retatrutide differ from the other compounds in this class?

It acts at GIP + GLP-1 + glucagon. The nearest alternatives act elsewhere: Tirzepatide (GIP + GLP-1), Semaglutide (GLP-1 alone), Liraglutide (GLP-1 alone), Cagrilintide (amylin), Survodutide (glucagon + GLP-1), Mazdutide (glucagon + GLP-1), VK2735 (GIP + GLP-1), Zenagamtide (GLP-1 + amylin), Pemvidutide (glucagon + GLP-1). Adding or removing a receptor changes both the effect and how much of it people can tolerate, so these molecules are not swappable at the same number of milligrams. Comparing them milligram for milligram is the most common mistake in this category.

What is not known about Retatrutide?

One trial cannot prove long-term safety or show that the result applies to everyone. The highest dose tested is a study dose, not a target for personal use.

For this compound specifically: At 48 weeks, the groups lost 8.7% of their starting weight at 1 mg and 24.2% at 12 mg, on average. The 4 mg and 8 mg groups lost 17.1% and 22.8%. The placebo group lost 2.1%.

Is there a Retatrutide dosing schedule on this site?

Not a schedule — there is no approved schedule to publish here. What you get instead is the trial dosing program: the doses each arm received and how the protocol worked up to them. The studied range was 1–12 mg once a week. See what the trials tested.

7primary sources, each with the day we read it — open the documents used on this page