DOSING IN THE TRIAL RECORD
The doses studied, and the titration schedules used
Retatrutide is investigational. The following summarises doses administered in the published clinical trial program; it is not prescribing guidance.
The short version
Retatrutide is investigational — it has no approved label, no approved dose, and is not legally prescribable outside a clinical trial. Everything on this page describes how the compound was administered to participants in published research protocols. It is not prescribing guidance.
The studied dose range ran from 0.5 mg to 12 mg, administered by subcutaneous injection once weekly. Phase 2 trials used 1, 4, 8, and 12 mg with stepwise escalation; Phase 3 TRIUMPH adds intermediate steps (2, 4, 6, 9, 12 mg). The stepwise approach exists specifically to manage gastrointestinal tolerability — GI events cluster during dose escalation and are dose-dependent. Adverse-event-driven discontinuation reached 16-18% at 12 mg across trials. No oral, intramuscular, or intranasal route has been clinically evaluated.
Regulatory status
Retatrutide is investigational. It is not approved by the FDA, the EMA, or any other regulatory authority as of 2026 [15][17]. It is not legally prescribable for obesity, type 2 diabetes, or any other indication outside an enrolled clinical trial.
Because no regulator has issued a label, no labelled indications, contraindications, dose ranges, or titration schedules exist. Everything in this section describes how the molecule was administered to participants in published research protocols. It is not, and cannot be, prescribing guidance.
Doses studied across the program
The first-in-human Phase 1 single-ascending-dose work in healthy adults explored a 0.1 mg to 12 mg range [17]. The Phase 1b multiple-ascending-dose study in adults with type 2 diabetes evaluated weekly doses from 0.5 mg up to 12 mg for 12 weeks [6].
The Phase 2 obesity trial (Jastreboff 2023) used four target weekly doses: 1, 4, 8, and 12 mg, with stepwise escalation [1]. The Phase 2 type 2 diabetes trial (Rosenstock 2023) used 0.5, 4, 8, and 12 mg weekly with both fast and slow escalation arms [5]. The Phase 2a MASLD substudy used the same 1, 4, 8, 12 mg structure over 48 weeks [7].
The Phase 3 TRIUMPH program added intermediate steps. TRIUMPH-1 reported on 4, 9, and 12 mg arms over 80 weeks [10]. TRIUMPH-4 reported on 9 and 12 mg arms over 68 weeks [12]. The master TRIUMPH protocol uses 2, 4, 6, 9, and 12 mg as the stepwise escalation ladder [17].
Pharmacokinetics and frequency
All published clinical studies have administered retatrutide once weekly by subcutaneous injection [17]. The apparent terminal half-life is approximately six days (around 144 hours), with linear and dose-proportional pharmacokinetics [6]. Albumin binding via the C20 fatty di-acid moiety extends circulating half-life; subcutaneous absorption is slow; steady state is typically reached after several weekly doses [6][17].
No other route — oral, intramuscular, intranasal — has been clinically evaluated. Trial supply was stored refrigerated.
Why titration matters
Gastrointestinal events are the most common adverse events across the trial program, are dose-dependent, and cluster during the escalation period rather than at maintenance [3]. In the Phase 2 type 2 diabetes trial, slow-escalation arms had improved tolerability compared with fast-escalation arms at the same final dose [5].
In Phase 2, adverse-event-driven discontinuation rose with dose: 6% at 1 mg, scaling to 16% at 12 mg, versus 0% on placebo [3]. In TRIUMPH-4 it was 12.2% on 9 mg and 18.2% on 12 mg versus 4.0% on placebo [13]. The TRIUMPH master escalation schedule (2 → 4 → 6 → 9 → 12 mg) is structured to ease tolerability at the cost of slower time-to-target dose.
Populations not yet studied
Retatrutide has not been evaluated in pregnancy, breastfeeding, or pediatric populations and is not authorised in any of these groups [17]. All Phase 2 and Phase 3 evidence to date is in adults.
The Phase 3 program enrols adults with obesity, type 2 diabetes, MASLD, established cardiovascular disease, knee osteoarthritis with obesity, and chronic kidney disease [17]. Each study has its own inclusion and exclusion criteria; the published topline figures from TRIUMPH-1 and TRIUMPH-4 describe outcomes within the specific enrolled populations and should not be extrapolated outside them.
What is not characterised at scale
Long-term safety beyond approximately two years is unknown [17]. The TRIUMPH-1 104-week extension is the longest published follow-up to date and was restricted to a subset of participants with baseline BMI ≥35 [11].
The portion of weight loss that is lean rather than fat mass has been characterised in a Phase 2 substudy and appears comparable to other incretin therapies [9]. The long-term functional consequences — sarcopenia risk in older adults, bone-mineral-density changes at this magnitude of weight loss — are not yet characterised.
Whether dysesthesia at the magnitude reported in TRIUMPH-4 (20.9% on 12 mg) persists, resolves on dose reduction, or extends to other phenotypes is under further evaluation [13].