How retatrutide was *dosed* in the trials

Before the numbers

This page documents the doses, schedules, and titration ladders studied in the published retatrutide clinical trials. It is a research record, not a dosing guide. Retatrutide has no FDA-approved dose because it has no FDA approval — there is no label, no prescribing information, no authorized protocol outside an investigator-supervised trial. What follows describes how the compound was administered in clinical research settings to participants with defined eligibility criteria and continuous medical monitoring. The reported doses run from 0.5 mg up to 12 mg once weekly by subcutaneous injection, with stepwise escalation built into every trial design. The numbers are here because they are in the published literature, and readers who arrive at a domain with 'script' in the name deserve an honest account of what that literature says. For the regulatory framework — why those doses cannot be replicated outside a trial — see the research page and the FAQ.

A note before the numbers

Retatrutide has no FDA-approved dose because it has no FDA approval. There is no label. There is no prescribing information. Everything below describes how the compound was administered in published clinical trials, under investigator supervision, in tightly defined patient populations, with intensive monitoring. None of it is a recommendation for use outside a trial. The descriptions are included because readers arriving at a domain with 'script' in the name reasonably want to understand what the research literature actually says.

For the regulatory framing, see /research and /faq.

Route and schedule

Every reported clinical trial has used subcutaneous injection — the abdomen, thigh, or upper arm — administered once weekly ^[5]. No oral, intramuscular, or intravenous formulation has been studied clinically. The once-weekly schedule is supported by a plasma half-life of approximately 6 days (range 5–7 days across reported pharmacokinetic studies), which in turn is enabled by reversible albumin binding through the C20 fatty-diacid linker ^[6].

The N-terminal aminoisobutyric-acid (Aib) substitution renders the peptide resistant to DPP-IV cleavage, the enzymatic mechanism that ordinarily clears native GLP-1 within minutes. The combination — fatty-acid albumin tether plus DPP-IV-resistant backbone — is the same engineering pattern used in semaglutide and tirzepatide, tuned in retatrutide's case to support a roughly weekly cadence at therapeutic concentrations across the studied dose range.

Dose ranges studied

Five distinct dose-finding windows appear in the literature.

The Phase 1 single-ascending-dose work in healthy volunteers used single doses from 0.1 mg through 8 mg subcutaneously ^[6]. The Phase 1b multiple-ascending-dose trial in type 2 diabetes used weekly doses from 0.5 mg through 12 mg over 12 weeks with stepwise titration ^[5]. The Phase 2 obesity trial randomized to 1, 2, 4, 8, or 12 mg weekly, with target doses reached via a 4-mg-per-4-week escalation schedule ^[1]. The Phase 2 type 2 diabetes trial used 0.5, 4, 8, and 12 mg weekly arms against dulaglutide 1.5 mg and placebo ^[3]. The Phase 3 TRIUMPH-4 trial used fixed 9 mg and 12 mg arms after a titration period ^[8].

What the literature does not describe is any 'maintenance' dose, any 'starter' dose for clinical use, or any titration schedule outside an investigator-supervised research protocol.

Titration

Across the Phase 2 and Phase 3 trials, retatrutide was introduced at a low dose (typically 2 mg) and escalated stepwise toward the assigned target. The escalation schedule used in the Phase 2 obesity trial was an additional 4 mg every 4 weeks until the cohort's target was reached ^[1]. The rationale is the same one that applies to other incretin agonists — most of the gastrointestinal adverse events cluster in the first 16 weeks of titration, and slow escalation lets the patient adapt to the appetite and gastric-emptying effects.

Nausea was reported in 36% of participants on the 1 mg arm and 59% on the 12 mg arm in the Phase 2 obesity trial ^[9]. Vomiting ranged from 8% to 39%. Most events were mild or moderate. Treatment-discontinuation rates ranged from 6% to 16% across the dose cohorts.

A dose-dependent transient rise in resting heart rate has also been reported — roughly +6.7 bpm at the 12 mg dose at 24 weeks, then drifting back toward baseline through weeks 36–48 ^[10].

Stability and handling in research settings

Retatrutide is supplied as a lyophilized peptide in research-trial materials and is reconstituted at the trial pharmacy before administration. Full stability data, expiry windows, and storage temperatures for any compounded or vendor-supplied material are not in the public peer-reviewed literature, because there is no public peer-reviewed literature on non-investigator-supplied material. Sites or vendors that publish 'reconstitution' protocols for retatrutide are not working from FDA-reviewed stability data — they cannot be, because none exists for material outside the sponsor's clinical-trial supply chain.

The practical takeaway: any dose, schedule, or reconstitution protocol that appears online for non-trial retatrutide is, at best, extrapolation from the Phase 2 trial publications, and at worst guesswork. The trial protocols themselves are public on ClinicalTrials.gov ^[11][12].

Why no 'starting dose' is given here

This site does not name a starting dose, a target dose, or a titration schedule for retatrutide outside the trial context, because doing so would imply that there is a known-safe protocol for use outside an investigator-supervised trial. There is not.

This is not a hedge for legal reasons. It is the actual state of the evidence. The Phase 3 program (TRIUMPH-1 through TRIUMPH-5) is what will generate the data on which a regulatory label is eventually written. Until those readouts arrive and the FDA review concludes, the 'right' dose outside a trial is not a question the literature can answer.

It is worth noting how unusual the dose-response in the Phase 2 obesity trial was. Across the 1, 4, 8, and 12 mg arms, the 24-week weight-loss curve had not plateaued at any cohort ^[2]. Most weight-loss drug programs see clear flattening at the top of the dose range. Retatrutide did not. That is one of the reasons the Phase 3 program is testing 9 mg and 12 mg as the working doses — the upper end is where most of the differentiating effect appears.