# Retatrutide Dosage: What the Clinical Trials Studied > Retatrutide dosage studied in Phase 1 through Phase 3 trials: once-weekly subcutaneous injection, dose escalation schedules, half-life pharmacokinetics, routes, and stability notes. Not dosing guidance. This page documents retatrutide dosage as study-design facts from published trials. It is not a dosing guide and does not provide any personal recommendation. ## The short version In every retatrutide trial to date, the compound has been given as a subcutaneous injection (injected under the skin) once a week. The trials tested amounts ranging from 0.5 mg up to 12 mg. Most participants started at a low amount and stepped up gradually over several weeks — a process called dose escalation — to reduce gastrointestinal side effects like nausea and vomiting. The 12 mg weekly dose produced the largest weight reductions and the most GI side effects in the Phase 2 obesity trial [1]. Retatrutide has a half-life of roughly six days — meaning its concentration in the blood drops by half about every six days — which is what makes weekly dosing feasible [4]. This page documents retatrutide dosage as trial design facts from published studies. It is not a dosing guide. There is no approved formulation and no approved dose — retatrutide is still investigational, not on prescription. ## Retatrutide dosage across trials **Phase 1b (Urva S et al., Lancet 2022):** Participants with type 2 diabetes received once-weekly subcutaneous injections across five dose cohorts: 0.5, 1.5, 3, 3→6, and 3→6→9→12 mg over 12 weeks. The stepwise escalation within the highest cohort (3 mg for 4 weeks, then 6 mg for 4 weeks, then 9 mg for 2 weeks, then 12 mg) established the tolerability and PK profile that informed Phase 2 design [4]. **Phase 2 obesity (Jastreboff AM et al., N Engl J Med 2023):** Adults with obesity received once-weekly subcutaneous doses of 1, 4, 8, or 12 mg for 48 weeks, with escalation built into each arm (e.g., the 12 mg arm began at a lower dose and stepped up). The dose-response relationship was steep: the 12 mg arm produced a mean −24.2% body-weight change versus −8.7% at 1 mg [1]. **Phase 2 T2D (Rosenstock J et al., Lancet 2023):** Doses from 0.5 to 12 mg once weekly with stepwise escalation, over 36 weeks. HbA1c reductions were dose-graded, with −2.02% at 12 mg [2]. **Phase 2 MASLD (Sanyal AJ et al., Nature Medicine 2024):** Once-weekly subcutaneous doses of 1, 4, 8, or 12 mg for 48 weeks. Liver fat reductions were dose-graded, with −82.4% relative change at 12 mg at 24 weeks [5]. **Phase 3 TRANSCEND-T2D-1 (Bajaj HS et al., Lancet 2026):** The first Phase 3 result used 12 mg once weekly in adults with type 2 diabetes over 40 weeks, confirming significant HbA1c and weight reductions [12]. ## How to reconstitute retatrutide Retatrutide has been studied exclusively as a clinical-trial investigational product supplied in pre-specified, pre-verified formulations under controlled conditions. There is no approved formulation, no approved reconstitution standard, and no published pharmaceutical-quality reconstitution protocol for any non-trial preparation. Search queries about how to reconstitute retatrutide or how to mix retatrutide with bacteriostatic water reflect the existence of lyophilized (freeze-dried) peptide preparations sold through unregulated research channels. This site does not provide reconstitution guidance for such preparations because doing so would imply a level of quality and identity verification that does not exist for gray-market peptides. There is no way to confirm that an unlabeled vial of research-grade material contains retatrutide at the stated concentration, or any retatrutide at all. In clinical trials, retatrutide was administered by trained staff under sterile conditions, with the drug's identity, concentration, sterility, and endotoxin levels confirmed to pharmaceutical standards before use. ## How often do you take retatrutide — the trial schedule In every completed trial, retatrutide was administered subcutaneously once weekly. The once-weekly schedule is pharmacokinetically supported by the compound's approximately 6-day half-life [4]: a single weekly injection maintains near-steady-state plasma concentrations between doses, without the peak-trough swings associated with daily injection schedules. **What is the Retatrutide dosage schedule?** In Phase 2 trials, standard practice was a multi-step escalation: lower amounts in the first 4–8 weeks, stepping up to the target amount thereafter. This is consistent with dose-escalation practice across the GLP-1 class — gradual increase reduces the severity of early GI adverse effects by allowing the gut to adapt before higher receptor activity is established. **How long does retatrutide take to work?** In the Phase 2 obesity trial, measurable weight changes were observable within the first 4–8 weeks at higher doses; the curve continued to descend through the full 48 weeks at 12 mg, with no plateau reached at the end of the trial, suggesting weight loss had not yet stabilized [1, 6]. A 2025 review characterizes this trajectory as distinctive compared to prior incretin agents [6]. ## Retatrutide cost and access — the research context Retatrutide cost is not publicly established because the compound is not a marketed product. No price list, formulary, or insurance coverage exists. Enrollment in a TRIUMPH trial is at no cost to participants. Gray-market research-channel retatrutide exists at widely varying prices. Those prices reflect unregulated supply-chain economics and carry no quality assurance. Gray-market preparations cannot be verified for identity, purity, or sterility. The FDA's 2025 enforcement actions against retatrutide vendors cited FD&C Act violations for selling an unapproved new drug. The cost of gray-market material is not a guide to clinical value or therapeutic equivalence. The most meaningful context for eventual retatrutide cost — if the compound reaches approval — is the pricing of approved dual-agonist agents in the same class, which have ranged from $900–$1,300/month in US list pricing before insurance. Retatrutide pricing, if approved, will be determined by regulatory status, competitive landscape, and payer negotiations that do not yet exist. ## How to store retatrutide — what the literature says Clinical-trial retatrutide was stored and distributed according to pharmaceutical cold-chain standards. No storage standard for gray-market preparations is available from published literature, because those preparations fall outside regulatory oversight. General principles from published GLP-1-class pharmaceutical literature suggest peptide-based injections are typically stored refrigerated (2–8°C) and protected from light. Whether any specific gray-market preparation behaves similarly to a pharmaceutical-grade formulation is unknown without independent stability testing. Stability data for retatrutide specifically have not been published outside of trial protocols. ## Retatrutide availability When will retatrutide be available? The honest answer is: it depends on Phase 3 trial outcomes and regulatory review timelines, neither of which are fixed. The TRIUMPH program trials (TRIUMPH-1, -2, -3) are ongoing as of mid-2026 [9, 10, 11]. The TRANSCEND-T2D-1 result published in Lancet 2026 is the first Phase 3 study to report [12]; it will contribute to a regulatory dossier alongside the TRIUMPH results. Regulatory applications would typically follow completion of pivotal trials, and approval review at FDA and EMA takes approximately 12 months from submission. A plausible estimated window — if trials read out and regulatory submissions are made promptly — is 2027–2028, but this is speculative. Retatrutide availability outside of trials currently means gray-market research-channel material, which this site does not recommend or link to. --- A digest of the published trial record — not a clinic, not a formulary, and not a prescription.