# Retatrutide Dosage in Clinical Trials — Research Digest > Retatrutide dosage studied in Phase 1b and Phase 2 trials: 1–12 mg once-weekly subcutaneous, half-life ~6 days. Research-context only — retatrutide is investigational, not approved. Research-context only. Retatrutide is investigational. Every figure here is a study-design fact from published trials, not a dosing recommendation. ## What this page covers Retatrutide is an investigational drug — it has not been approved by any regulator, and there is no standard dose. What follows is a plain-English summary of the doses researchers used in published clinical trials. These are study-design facts, not instructions. The appropriate doses for any person would be determined by a physician within a clinical trial, not sourced from a research digest. The figures on this page come from three published trial programs: the Phase 1b multiple-ascending-dose study [4], the Phase 2 obesity trial [1], and the Phase 2 type 2 diabetes trial [2]. ## Retatrutide dosage **Phase 1b (first-in-human, type 2 diabetes):** Five dose cohorts were studied — 0.5 mg, 1.5 mg, 3 mg, 3/6 mg (stepped), and 3/6/9/12 mg (stepped) — all administered once weekly by subcutaneous injection for 12 weeks [4]. This was the dose-escalation design used to establish tolerability and pharmacokinetics before advancing to larger trials. **Phase 2 obesity trial:** Four fixed dose groups — 1, 4, 8, and 12 mg once weekly subcutaneous for 48 weeks [1]. The dose-escalation periods within each group started at lower levels and increased over several weeks to manage gastrointestinal tolerability. **Phase 2 type 2 diabetes trial:** Stepwise escalation from 0.5 mg to a maximum of 12 mg once weekly over a multi-week ramp, with four final target doses: 1, 4, 8, and 12 mg [2]. Background diabetes medications were maintained at entry; insulin doses were adjusted downward as glycemic control improved. **Phase 3 (ongoing):** TRIUMPH-1 and the parallel trials use once-weekly subcutaneous administration; specific dose protocols have not been fully published as of mid-2026 [7][8][9][10]. ## Retatrutide half life Phase 1b pharmacokinetic data established a plasma half-life of approximately six days for retatrutide [4]. This half-life is achieved by the C20 fatty-diacid acylation of the peptide backbone, which promotes albumin binding and substantially slows renal and hepatic clearance — the same engineering approach used in other long-acting incretin therapeutics. A six-day half-life means that with weekly dosing, plasma concentrations reach a near-steady-state within three to four weeks and accumulate moderately above single-dose levels. Importantly, it also means that any adverse effects — including the documented heart-rate elevation and GI symptoms — will persist for days after a dose is given; there is no rapid off-switch. ## Retatrutide side effects — the clinical record In the Phase 2 obesity trial, the most common adverse events were gastrointestinal: nausea (up to 45 percent at 12 mg), vomiting, diarrhea, and constipation [1]. These were dose-related and most commonly mild to moderate in severity. Dose escalation — the practice of starting at a low amount and increasing gradually over weeks — was the primary strategy for managing GI effects in the trial design; 18 percent of 12 mg participants discontinued [1]. A dose-dependent increase in resting heart rate was recorded, with mean increases of approximately 5–7 bpm at the highest doses, peaking around 24 weeks [1]. Injection-site reactions occurred in approximately 8 percent of participants. No severe hypoglycemia was recorded in participants not on background insulin or sulfonylureas. In the Phase 2 diabetes trial, 35 percent of participants reported mild-to-moderate GI adverse events and no severe hypoglycemia or deaths occurred [2]. ## How to reconstitute retatrutide Retatrutide as used in clinical trials is a pharmaceutical-grade, GMP-manufactured, pre-formulated solution produced by Eli Lilly's clinical supply chain. There is no approved or standardized reconstitution protocol for research-labeled retatrutide because no approved consumer or clinical-supply product exists outside trial-controlled conditions. Any research-labeled material obtained outside a clinical trial is of unverified identity, purity, and sterility. The stability notes from the published trial program indicate retatrutide was studied only as a pre-formulated investigational product administered once weekly by subcutaneous injection; no official formulation, storage, or reconstitution standard exists for any non-trial preparation [1][4]. This site does not provide reconstitution instructions; doing so would be providing procedural guidance for an unapproved, unverified injectable compound outside any medical oversight. ## Retatrutide cost No commercial price exists for retatrutide because it is not approved for sale anywhere. Participants in clinical trials receive the compound at no cost as part of trial protocol. Research-labeled retatrutide sold through gray-market channels carries a market price set by unregulated vendors — a price that reflects neither pharmaceutical manufacturing standards nor any verified compound identity. A 2024 Clinical Diabetes profile and the broader trial literature do not discuss consumer pricing because the compound has not reached that stage of development [14]. Cost estimates circulating online for gray-market material should be evaluated with the understanding that the product's identity, purity, and sterility cannot be confirmed from those sources. ## Retatrutide vs tirzepatide Tirzepatide is a dual GIP/GLP-1 agonist that is FDA-approved for type 2 diabetes and obesity management. Retatrutide is an investigational triple agonist (GIP + GLP-1 + glucagon) that has not been approved. Comparing Phase 2 obesity trial data directly: tirzepatide produced approximately 15–21 percent body-weight reduction at its highest studied doses versus retatrutide's −24.2 percent at 48 weeks in Phase 2 [1]. However, these are different trials, different populations, different dose ramps — a direct cross-trial comparison cannot establish superiority. The active-comparator head-to-head trial (NCT06662383) is specifically designed to answer this question; it is ongoing and has not reported results [10]. The mechanistic hypothesis for retatrutide's additional weight reduction is the glucagon receptor arm driving thermogenic energy expenditure — a pathway tirzepatide's dual mechanism does not engage [1][6]. ## When will retatrutide be available No approval date has been announced by Eli Lilly or any regulatory agency. The TRIUMPH Phase 3 program is ongoing; typical Phase 3 durations are 18 to 36 months for obesity trials, followed by data analysis, regulatory submission, and review (typically 6–12 months for a standard NDA, faster if a Breakthrough Therapy or Priority Review designation applies). Retatrutide has received Fast Track designation from the FDA, which can accelerate review timelines but does not guarantee approval. Regulatory submission has not yet been announced as of mid-2026. For a full breakdown of the trial timeline and what regulatory steps remain, see the [retatrutide availability](/availability) page. --- A broadsheet digest of the published clinical trial record — not a clinic, not a prescription service, not a vendor.