How is retatrutide dosed?
Retatrutide has no FDA-approved product and no prescribing information, so there is no label schedule to read. This page reads the Phase 2 and Phase 3 TRIUMPH trial doses directly instead — the NCT number, phase, enrollment, and arms for each trial, with the adverse events reported alongside the dose that produced them.
Topic: Reading retatrutide’s trial doses directly, since no label exists
Audience: Anyone comparing a retatrutide dose figure against its actual trial source
Reading time: 8–10 minutes
No approved product exists
Retatrutide has not been approved by the FDA, EMA, or any other major regulatory body, under any brand name, for any indication. There is no prescribing information, no boxed warning, and no approved dosage to defer to. Every figure on this page is a fact about a specific clinical trial — not a recommendation, and not a substitute for an approved product that does not exist.
On this page
What retatrutide is, and what it isn’t
Retatrutide (LY3437943) is Eli Lilly’s investigational triple receptor agonist, activating receptors for glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon. It has been studied in Phase 2 and Phase 3 trials across obesity, type 2 diabetes, knee osteoarthritis, obstructive sleep apnea, and metabolic dysfunction-associated steatotic liver disease. None of that trial activity has produced an approved product: as of this page’s build, retatrutide has no brand name, no NDA approval, and no regulatory filing decision from the FDA.
That is the structural reason this page reads differently from how Prof. Peptide reads Mounjaro’s label or Ozempic’s, Wegovy’s, and Zepbound’s. Those pages report what an approved product’s own prescribing information states. Retatrutide has no such document, so what follows is a report of what each trial itself administered and found — not a schedule. The Prof. Peptide retatrutide profile covers the mechanism and broader research areas in more depth; this page exists specifically to read the trial doses and their reported adverse events side by side.
What the trials administered
Five trials met the bar for inclusion here: each has a checkable NCT number, a published or company-reported phase, enrollment, and dose arms, and an endpoint result attributable to a specific document. Each trial is graded against Prof. Peptide’s standing citation convention — a claim is attributed when it resolves to a named, checkable source. All five grade as attributed, though three (TRIUMPH-1, TRIUMPH-4, TRANSCEND-T2D-1) are reported from Lilly’s own topline release rather than a peer-reviewed publication as of this page’s build, and are marked as such below — a topline company release and a peer-reviewed paper are not the same kind of source, even when both are attributable.
Phase 2 — Obesity
NCT04881760Jastreboff AM, Kaplan LM, Friías JP, et al. N Engl J Med. 2023;389:514–526.
Design: 48-week, randomized, double-blind, placebo-controlled trial in adults with a BMI of 30 or higher, or 27 to under 30 with at least one weight-related condition.
Arms: Placebo (N=70), retatrutide 1 mg (N=69), 4 mg (N=67), 8 mg (N=70), 12 mg (N=62) — higher-dose arms used a 2 mg or 4 mg starting dose with escalation to target over the first 4–12 weeks.
Endpoint reported: Least-squares mean body-weight change at 24 weeks: −1.6% (placebo) vs. −7.2% (1 mg), −12.9% (4 mg), −17.3% (8 mg), −17.5% (12 mg). At 48 weeks, the 12 mg arm reached a mean reduction of 24.2%.
Adverse events reported at these doses: Overall adverse events were reported in 70% of the placebo group versus 73%–94% across retatrutide arms, highest at 8 mg and 12 mg. Nausea rose from 14% (1 mg) to 47% (12 mg); vomiting was reported in 21% at 12 mg. Most gastrointestinal events were mild to moderate and occurred during the escalation weeks. The serious adverse event rate was 4% across all retatrutide arms — the same as placebo.
Attributed — published in a peer-reviewed journal, registered with a checkable NCT number, phase/N/arms independently confirmed against the ClinicalTrials.gov record.
Phase 2 — Type 2 Diabetes
NCT04867785Rosenstock J, Frías J, Jastreboff AM, et al. Lancet. 2023;402:529–544.
Design: 36-week, randomized, double-blind, double-dummy, placebo- and active-controlled trial in adults with type 2 diabetes inadequately controlled by diet and exercise, conducted at 42 US sites.
Arms: Placebo, dulaglutide 1.5 mg (active comparator), and retatrutide at 0.5 mg, 4 mg, 8 mg, and 12 mg — the 4 mg and 8 mg arms each split between two starting-dose escalation strategies, N=281 total.
Endpoint reported: HbA1c reduction of up to 2.0% and body-weight reduction of up to 16.9% at 36 weeks in the highest-dose arms; roughly 80% of participants assigned retatrutide reached a target HbA1c of 7% or below.
Adverse events reported at these doses: Safety profile was consistent with the GLP-1 and dual GIP/GLP-1 receptor agonist class — gastrointestinal events dominant and dose-related, per the trial's published safety conclusion. This page does not carry a per-dose breakdown for this trial specifically, since the publication's tables were not independently re-verified line by line before this page was built.
Attributed — published in a peer-reviewed journal, registered with a checkable NCT number, phase/N confirmed against the ClinicalTrials.gov record.
TRIUMPH-1 — Phase 3, Obesity
NCT05929066Eli Lilly and Company, topline results announcement, 2025.
Design: Phase 3, multicenter, randomized, double-blind, placebo-controlled trial in adults without type 2 diabetes who have obesity or overweight with at least one weight-related comorbidity. Master-protocol design, with sleep-apnea and knee-osteoarthritis sub-populations nested inside it.
Arms: 2,335 participants (actual enrollment, per the registry) randomized to placebo or retatrutide 4 mg, 9 mg, or 12 mg, with stepwise titration from a 2 mg starting dose every 4 weeks to target.
Endpoint reported: Mean body-weight change at week 80 (efficacy estimand): −2.2% (placebo), −19.0% (4 mg), −25.9% (9 mg), −28.3% (12 mg).
Adverse events reported at these doses: Discontinuation due to adverse events: 4.9% (placebo), 4.1% (4 mg), 6.9% (9 mg), 11.3% (12 mg). At the 12 mg dose: nausea 42.4%, diarrhea 32.0%, constipation 26.1%, vomiting 25.3%, dysesthesia 12.5%. Lilly's release describes dysesthesia and urinary tract infection events as generally mild to moderate, mostly resolving during treatment.
Attributed — phase, N, and arms confirmed directly against the ClinicalTrials.gov record (status: completed, primary completion April 2026). Efficacy and AE figures are Lilly's own topline release, not yet a peer-reviewed publication as of this page's build — flagged as topline, not final, for that reason.
TRIUMPH-4 — Phase 3, Obesity + Knee Osteoarthritis
NCT05931367Eli Lilly and Company, topline results announcement, December 2025.
Design: Phase 3, randomized, double-blind, placebo-controlled trial in adults with obesity or overweight and osteoarthritis of the knee. Co-primary endpoints: percent body-weight change and WOMAC pain subscale change, both at week 68.
Arms: 445 participants randomized 1:1:1 to placebo, retatrutide 9 mg, or retatrutide 12 mg — the registry does not publish an exact per-arm N breakdown.
Endpoint reported: Body-weight change at week 68 (efficacy estimand): −2.1% (placebo), −26.4% (9 mg), −28.7% (12 mg). WOMAC pain subscale decreased 2.4 points (placebo), 4.5 points (9 mg), 4.4 points (12 mg).
Adverse events reported at these doses: Discontinuation due to adverse events: 4% (placebo), 12.2% (9 mg), 18.2% (12 mg). Dysesthesia: 0.7% (placebo), 8.8% (9 mg), 20.9% (12 mg). Most common adverse events overall were nausea, diarrhea, constipation, vomiting, and decreased appetite — all more frequent than placebo.
Attributed — phase, N, and arms confirmed directly against the ClinicalTrials.gov record (status: completed, actual completion November 2025). Efficacy and AE figures are Lilly's own topline release, flagged as topline rather than a peer-reviewed publication for the same reason as TRIUMPH-1.
TRANSCEND-T2D-1 — Phase 3, Type 2 Diabetes
NCT06354660Eli Lilly and Company, topline results announcement, March 2026; Lancet publication pending as of this page's build.
Design: 40-week, randomized, multicenter, double-blind, placebo-controlled trial at 48 sites in the US, Mexico, and India, in adults with type 2 diabetes inadequately controlled by diet and exercise (HbA1c 7.0–9.5%, BMI ≥ 23 kg/m²).
Arms: 537 participants randomized 1:1:1:1 to placebo or retatrutide 4 mg, 9 mg, or 12 mg, once-weekly subcutaneous injection.
Endpoint reported: HbA1c reduction of 1.7% to 2.0% across the three retatrutide doses at week 40; the 12 mg arm lost a mean of 16.8% body weight (about 36.6 lb).
Adverse events reported at these doses: Nausea: 3.7% (placebo), 16.4% (4 mg), 19.5% (9 mg), 26.5% (12 mg). Diarrhea: 4.5%, 18.7%, 26.3%, 22.8%. Vomiting: 2.2%, 15.7%, 15.0%, 17.6%. Discontinuation due to adverse events: 0.0%, 2.2%, 4.5%, 5.1%. Dysesthesia: 0.0%, 4.5%, 2.3%, 4.4%.
Attributed — phase, N, and arms confirmed directly against the ClinicalTrials.gov record (status: completed). Efficacy and AE figures are Lilly's own topline release; a Lancet peer-reviewed publication is listed but was not independently re-read for this page.
Is there a community-reported dose?
Prof. Peptide looked for a genuinely reportable community dosing convention — a figure attributed to a specific, checkable source describing what researchers or users actually report doing, the way some other profiles on this site attribute a bedtime-dosing convention or a cycling pattern to a named practice. None was found for retatrutide.
Sources describing a “typical” or “commonly cited” retatrutide starting dose conflict directly with each other — 0.5 mg, 1 mg, 2 mg, and 2.5 mg each appear as “the” starting dose on different vendor and blog pages — and each one turns out to be either a restatement of one specific trial’s own escalation schedule under different language, or a number with no source behind it at all. Neither is a community convention distinct from the trial data already reported above, so nothing is presented as one here.
Compounding and research-grade retatrutide
There is no approved retatrutide product, so there is neither a branded version nor a lawful pharmacy-compounded version of one — a simpler and stricter boundary than semaglutide’s or tirzepatide’s.
FDA’s own warning letter on the subject, addressed to a compounding pharmacy and dated September 9, 2025, states: “Drug products compounded using retatrutide are not eligible for the exemptions provided by section 503A, because retatrutide is not the subject of an applicable USP or NF monograph, is not a component of an FDA-approved human drug, and does not appear on the 503A bulks list,” and separately, “are not eligible for the exemptions provided by section 503B, because retatrutide does not appear on the 503B bulks list, and is not used to compound a drug that appears on the drug shortage list.”
That is a different regulatory situation from semaglutide and tirzepatide during their supply shortages. Both of those had an approved brand-name product already on the market, which is what opened a temporary compounding pathway under sections 503A and 503B once the drug appeared on FDA’s drug shortage list. Retatrutide was never an approved product, so it was never eligible for that pathway in the first place — the shortage-driven compounding history that applies to the GLP-1 class generally does not extend to a molecule with no approval to begin with.
FDA does operate one sanctioned, non-trial route to human use: a pre-approval expanded-access (compassionate use) program, registered on ClinicalTrials.gov, limited to adults with severe obesity (BMI 35 kg/m² or higher) and at least two serious obesity-related complications who have exhausted approved treatment options. That program is requested through a physician and Eli Lilly directly — it is not something Prof. Peptide’s vendors are part of, and it is unrelated to the research-grade material described below.
Research-grade retatrutide, of the kind sold by the vendors Prof. Peptide tracks elsewhere on this site, is not a compounded drug product, not the expanded-access product, and not a branded product — those categories don’t apply to it at all. It is sold labeled for laboratory research use, not for human administration, and it is not dispensed against a prescription.
FAQ
Is there an FDA-approved retatrutide product?
What dose did the Phase 3 TRIUMPH trials use?
Is there a commonly reported retatrutide starting dose outside the trials?
What were the most common side effects in the trials?
Can retatrutide legally be compounded like semaglutide or tirzepatide once were?
What does Prof. Peptide's own research-grade retatrutide fall under, then?
References
- Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389:514–526. ClinicalTrials.gov NCT04881760. https://clinicaltrials.gov/study/NCT04881760
- Rosenstock J, Frías J, Jastreboff AM, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes. Lancet. 2023;402:529–544. ClinicalTrials.gov NCT04867785. https://clinicaltrials.gov/study/NCT04867785
- ClinicalTrials.gov. A Master Protocol to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants Without Type 2 Diabetes Who Have Obesity or Overweight (TRIUMPH-1), NCT05929066. https://clinicaltrials.gov/study/NCT05929066
- ClinicalTrials.gov. A Phase 3 Study to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants Who Have Obesity or Overweight and Osteoarthritis of the Knee (TRIUMPH-4), NCT05931367. https://clinicaltrials.gov/study/NCT05931367
- ClinicalTrials.gov. A Phase 3 Study to Investigate the Efficacy and Safety of Retatrutide Once Weekly Compared With Placebo in Adult Participants With Type 2 Diabetes (TRANSCEND-T2D-1), NCT06354660. https://clinicaltrials.gov/study/NCT06354660
- U.S. Food and Drug Administration. Warning Letter: GLP-1 Solution, reference 715883, 2025-09-09. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/glp-1-solution-715883-09092025
- ClinicalTrials.gov. Pre-approval Expanded Access of Retatrutide (LY3437943), NCT07629401. https://clinicaltrials.gov/study/NCT07629401
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