# Retatrutide Dosage in Clinical Trials: Schedules, Escalation, and Study Context > Retatrutide dosage as measured in clinical trials: 1–12 mg once-weekly subcutaneous injection with escalation protocols. Trial design facts from Phase 1b and Phase 2 — not dosing instructions. Phase 1b and Phase 2 dose ranges, escalation protocols, and the pharmacokinetic rationale for once-weekly administration — reported as study design, not instruction. ## The short version Retatrutide dosage information on this page is reported as trial design fact — what researchers administered to which population at which amount and schedule, and what they found. This is not a dosing guide. Retatrutide is investigational, not approved, and there is no labeled dose. The core dosing pattern across Phase 2 trials: subcutaneous injection (injected into the fatty layer under the skin) once weekly, starting at a low amount and escalating gradually to allow the body to adapt to GI side effects. The Phase 2 obesity trial tested 1 mg, 4 mg, 8 mg, and 12 mg weekly doses. Phase 1b used an ascending sequence starting at 0.5 mg and stepping up to 12 mg. The ~6-day half-life of retatrutide — how long it takes for half the compound to clear the blood — is what makes once-weekly dosing possible. Full pharmacokinetics are on the [retatrutide half life](/half-life) page. ## Retatrutide dosage Trial doses studied in humans [1][2][4]: **Phase 1b (12 weeks, type 2 diabetes adults, n=72):** 0.5, 1.5, 3, 3/6, and 3/6/9/12 mg subcutaneous once weekly. The ascending sequences (3/6 and 3/6/9/12 mg) represent titration steps — participants started at the lower amount and escalated to the next level on a defined schedule. **Phase 2 obesity (48 weeks, adults with obesity, n=338):** Fixed doses of 1, 4, 8, or 12 mg subcutaneous once weekly. All doses were initiated at a starting level and escalated within each arm over multiple weeks. **Phase 2 type 2 diabetes (36 weeks, n=281):** 0.5 mg escalating to 12 mg subcutaneous once weekly in stepwise increments. The dose-response relationship in Phase 2 obesity was steep: -8.7% (1 mg), -17.3% (4 mg), -22.8% (8 mg), -24.2% (12 mg) body-weight change versus -2.1% for placebo [1]. Dose escalation is not optional in trial design — it is the primary strategy for managing GI adverse events. Reviews confirm that slow up-titration reduces nausea burden across the GLP-1 class [7]. ## Retatrutide side effects in dose context Adverse events from the Phase 2 obesity trial were dose-related [1]: - Nausea: affected ~23% at 1 mg, rising to ~45% at 12 mg. - Vomiting: 12–28% across the dose range. - Diarrhea: 12–20%. - Constipation: 12–22%. - Discontinuations due to AEs: 3% (1 mg) to 18% (12 mg). - Heart-rate increase: dose-dependent, peaking at ~24 weeks; mean increase ~5–7 bpm at highest doses. - Injection-site reactions: ~8%. No severe hypoglycemia. No deaths in the Phase 2 program. GI events were mostly mild-moderate and improved with time in participants who stayed in the trial. For the community signal data — what people using research-labeled retatrutide outside trials report — see [Retatrutide effects](/effects). ## How to reconstitute retatrutide This is a common search question. The direct answer: there is no approved reconstitution protocol for retatrutide. In Phase 2 and Phase 3 trials, retatrutide was supplied as a pre-formulated single-use prefilled pen or syringe by the manufacturer (Eli Lilly) under clinical-trial GMP (good manufacturing practice) conditions. Participants did not reconstitute it themselves. The stability note from the compound record: retatrutide was studied only as a clinical-trial investigational product administered by once-weekly subcutaneous injection. No approved formulation, storage temperature, diluent specification, or reconstitution standard exists for any non-trial preparation. Gray-market research-labeled retatrutide typically arrives as a lyophilized (freeze-dried) powder. Any reconstitution instruction circulating for such products is not derived from approved labeling — it does not exist. It is community convention applied to an unregulated, unverified product. ## Retatrutide availability Retatrutide is not commercially available. It is not a prescription drug. There is no approved indication and no regulatory approval in any country as of mid-2026. Access pathways that currently exist: 1. **Clinical trial enrollment** — TRIUMPH Phase 3 trials are enrolling eligible participants in multiple countries. ClinicalTrials.gov lists active sites. 2. **Gray-market research-labeled material** — unregulated, unverified, and outside any clinical oversight. Identity, purity, and sterility cannot be confirmed. There is no third option. ## When will retatrutide be available No regulatory filing date has been announced by Eli Lilly as of mid-2026. Phase 3 TRIUMPH trials are running. Regulatory submission typically requires completed Phase 3 data plus a full manufacturing and safety package — a process that, for a novel drug, takes a minimum of one to three years after trial completion. The earliest realistic scenario for a retatrutide approval in the United States would be late 2026 to 2027, assuming trial completion and rapid regulatory review — neither of which is guaranteed. Phase 3 trial completion dates listed on ClinicalTrials.gov (NCT05929066, NCT05931367, NCT06383390) are the authoritative public estimate source. --- A no-vendor reading of the retatrutide trial record — Phase 2 numbers read straight from the source, Phase 3 gaps named as gaps, and nothing here scripted, dispensed, or sold.