Retatrutide

Not FDA-approved Evidence grade B — human randomised trials, not approved for that use Updated 2026-10-20

This page describes published research and public regulatory records. It is not medical advice. SoluneFit does not sell, supply, or recommend any compound. The SoluneFit app includes a private, on-device tracker for people who want a record of what they and their clinician have already decided — the app neither suggests compounds nor doses.

Also known as: LY3437943, Reta, triple agonist.

Regulatory status

Not FDA-approved; investigational (Lilly phase 3 TRIUMPH programme) [3][4]. FDA warning letters of September 2025 to online sellers state that compounded retatrutide products are unapproved new drugs and misbranded, have no approved application, and are not eligible for the section 503A compounding exemptions [6].

What it is

Triple GIP, GLP-1 and glucagon receptor agonist (single synthetic peptide; investigational).

An investigational once-weekly injected peptide from Eli Lilly that activates the GIP, GLP-1 and glucagon receptors. Studied for obesity, type 2 diabetes, knee osteoarthritis pain and obstructive sleep apnoea; not approved anywhere.

What the published research shows

Phase 2 RCTs (338 adults with obesity; 281 with type 2 diabetes) and phase 3 RCTs published 2026 (TRIUMPH-1, 2,339 adults, 80 weeks; TRIUMPH-2, 1,152 adults with type 2 diabetes); no regulatory approval.

Published human studies and reports (these describe trial populations, not SoluneFit claims):

Obesity without diabetes (phase 2 trial, Jastreboff 2023): 338 adults, once-weekly SC retatrutide 1, 4, 8 or 12 mg (4 and 8 mg arms started at 2 or 4 mg; 12 mg started at 2 mg) or placebo for 48 weeks. Mean weight change at 48 weeks: -8.7 % (1 mg), -17.1 % (4 mg), -22.8 % (8 mg), -24.2 % (12 mg) versus -2.1 % placebo.
Type 2 diabetes (phase 2 trial, Rosenstock 2023): 281 adults, weekly doses 0.5-12 mg versus placebo or dulaglutide 1.5 mg. HbA1c fell up to 2.02 % at 24 weeks (12 mg) and body weight up to 16.94 % at 36 weeks.
Obesity with knee osteoarthritis or sleep apnoea subgroups (phase 3 TRIUMPH-1): 2,339 adults without diabetes, weekly 4, 9 or 12 mg or placebo for 80 weeks: mean weight change -17.6 %, -23.7 % and -25.0 % versus -3.9 % placebo; knee pain and apnoea-hypopnoea index also fell.
Obesity with type 2 diabetes (phase 3 TRIUMPH-2): 1,152 adults, weekly 4, 9 or 12 mg or placebo for 80 weeks: mean weight change -11.9 %, -16.8 % and -18.8 % versus -5.1 % placebo.

Mechanism, as reported

Combines the appetite and insulin effects of GIP and GLP-1 receptor activation with glucagon-receptor activation, which in mice added an increase in energy expenditure. Pharmacokinetics support once-weekly dosing.

Practical record

Elimination half-life: 144.0 h (confidence: medium). Phase 1b trial in type 2 diabetes: half-life approximately 6 days, dose-proportional pharmacokinetics. Coskun et al., Cell Metab 2022 (phase 1) says only that its PK supported weekly dosing (full text paywalled, not opened). No published volume of distribution.
Studied routes: subcutaneous.
Typical supply: No approved product; supplied only as investigational trial drug. Sold illegally online as 'research' vials, which FDA treats as unapproved new drugs.

Safety signals on record

Reported adverse events: Mostly dose-related gastrointestinal effects (nausea, diarrhoea, vomiting, constipation), partly reduced by a lower starting dose; dose-dependent heart-rate increase peaking around 24 weeks; in TRIUMPH-2, more hypotension and dysesthesia than placebo, and discontinuation for adverse events of 8-12 % at 9-12 mg.
Contraindications: None established (no label).
Interactions: None documented in a label. UNVERIFIED by label: as with other GLP-1 agonists, delayed gastric emptying could alter absorption of oral drugs.
Notes: Unapproved: any product outside a trial is unregulated, with unknown identity, purity and dose. Long-term safety beyond 80 weeks is not established.

Sources

General wellness education, not medical advice. Unapproved compounds have no established dosing, purity standard, or safety profile.

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