Retatrutide dosage as studied in Phase 1, 2, and 3 trials.

Before the details

This page summarizes how retatrutide was dosed in the clinical trials published through 2026. Nothing here is dosing advice — retatrutide is an investigational drug that is not approved for human use anywhere in the world, and no safe or effective dose is established for use outside a supervised clinical trial. The information below describes study design facts: what researchers administered, how, and for how long. That context helps a reader understand the pharmacology. It is not a protocol to follow.

Retatrutide dosage in the Phase 2 obesity trial

In the 48-week Phase 2 obesity trial published in the New England Journal of Medicine (Jastreboff 2023), participants received once-weekly subcutaneous retatrutide at one of four doses: 1 mg, 4 mg, 8 mg, or 12 mg ^[1]. The trial used a dose-escalation protocol (starting low and stepping up over several weeks) to reduce GI side effects during the initial adjustment period. The highest dose, 12 mg per week, produced the study's primary endpoint result: a mean body-weight change of -24.2% over 48 weeks.

All doses were administered by subcutaneous injection — injected into the layer of fat just beneath the skin — once per week. No other routes of administration have been studied in humans.

Retatrutide dosage in the Phase 2 type 2 diabetes trial

The Lancet Phase 2 trial in type 2 diabetes (Rosenstock 2023) used escalating doses from 0.5 mg up to 12 mg once weekly over 36 weeks ^[2]. The stepwise escalation — 0.5 mg, then 1.5 mg, then 3 mg, then 6 mg, then 12 mg — was designed to let the body adjust to each level before advancing, reducing GI adverse event burden.

HbA1c reduction was dose-dependent: higher doses produced larger blood-sugar improvements. At 12 mg/week, HbA1c fell by 2.02% at 24 weeks. Body weight fell by 16.94% at 36 weeks.

Retatrutide half life

Retatrutide's half-life in humans is approximately 6 days ^[4]. This was established in the Phase 1b pharmacokinetic study (Urva 2022) and is what makes once-weekly dosing possible. A 6-day half-life means the drug accumulates to a steady state over several weeks of once-weekly dosing, which is why the maximum effect in trials was typically observed at around 20-36 weeks rather than immediately.

The extended half-life results from a deliberate molecular design feature: the fatty-acid chain attached to the peptide causes it to bind reversibly to albumin (a blood protein), which dramatically slows its clearance from the bloodstream compared with native peptide hormones, which have half-lives measured in minutes.

How to reconstitute retatrutide

Retatrutide was administered in the clinical trials as a pre-formulated, clinical-grade investigational product. No approved formulation, standardized reconstitution recipe, or sterility standard exists for any non-trial preparation of retatrutide.

This is an important distinction: compounds sold on the gray market as "research retatrutide" are not pharmaceutical-grade retatrutide. They are not subject to the identity verification, potency testing, endotoxin testing, or sterility assurance that clinical trial materials must pass. There is no documented reconstitution protocol for these materials that has been validated for safety or efficacy. The stability notes from the research record apply only to the clinical-trial product; they do not transfer to gray-market material of unknown composition.

Retatrutide availability

Retatrutide is not commercially available anywhere in the world as of mid-2026. It remains an investigational new drug (IND) in Eli Lilly's TRIUMPH Phase 3 program. It cannot be prescribed and is not available in pharmacies.

The only legitimate way to receive retatrutide is through enrollment in a registered clinical trial — which requires meeting specific eligibility criteria, medical screening, and ongoing monitoring.

Gray-market "research" retatrutide sold outside clinical trials is unregulated, of unverified identity and purity, and outside any form of clinical oversight. The FDA issued warning letters to over 50 vendors of such material in 2025.

When will retatrutide be available

The timeline for potential regulatory approval depends on when the TRIUMPH Phase 3 trials complete and when Eli Lilly submits a New Drug Application (NDA). As of mid-2026, multiple Phase 3 trials are ongoing, including cardiovascular and renal outcomes studies that need to report before a regulatory submission is complete.

Analysts tracking Eli Lilly's pipeline have speculated about a 2026-2027 NDA submission timeline for some indications, but this is speculative and depends on unblinded trial results, regulatory dialogue, and manufacturing scale-up. No approval date has been announced. This site will not speculate on a commercial availability date; check Eli Lilly's official communications and ClinicalTrials.gov for current trial status.

Retatrutide cost

No commercial price for retatrutide exists, because it is not approved and has not been priced for the market. Pricing will depend on the indication approved, the market, the payer environment, and Eli Lilly's commercial strategy — none of which have been finalized.

For context: approved dual agonists in the same class are list-priced in the United States in the range of $900-$1,400 per month without insurance coverage, though actual out-of-pocket costs vary widely by insurance status and manufacturer assistance programs. Whether retatrutide would be priced similarly, more, or less is pure speculation at this point.

This site does not have pricing information and does not link to any source for obtaining retatrutide.