Retatrutide Dosage Chart: Trial Doses From 2 mg to 12 mg

Anyone searching for a retatrutide dosage chart runs into the same problem fast: the compound has never been approved for sale, yet the clinical trial record is detailed enough to chart precisely. This piece lays out exactly what the Phase 2 and Phase 3 trial arms tested, dose by dose and week by week, and where research-platform ladders line up with that record. No part of it is a prescribing instruction.

Key takeaways#

• The Phase 2 trial (NCT04881760) tested 1 mg, 4 mg, 8 mg and 12 mg weekly arms over 48 weeks; the 4 mg to 12 mg arms started at 2 mg or 4 mg and escalated.
• Phase 3 TRIUMPH-1 (NCT05929066) started every retatrutide arm at 2 mg weekly and stepped up every 4 weeks toward 4 mg, 9 mg, or 12 mg targets over 80 weeks.
• No regulator has approved a retatrutide dose. The compound remains investigational in every indication studied so far.
• Nausea rose from 28.6% on the 4 mg arm to 42.4% on the 12 mg arm in TRIUMPH-1, against 14.8% on placebo.
• Retatrutide's trial doses run on a different numeric scale than semaglutide's and overlap much of tirzepatide's injectable range, though its ceiling stays below tirzepatide's approved maximum.

Retatrutide has no FDA-approved dosage because it remains an investigational drug#

Retatrutide dosage refers only to the once-weekly injection amounts tested in Eli Lilly's trials, not an approved prescribing label. No regulatory agency has cleared any retatrutide dose for sale. Every number on a retatrutide dosage chart, from the 2 mg start to the 4 mg, 9 mg, and 12 mg maintenance targets, comes from trial protocols alone.

That status has not changed as the trial program has grown. Retatrutide (also called LY3437943) has moved through a Phase 2 obesity trial and a wave of Phase 3 TRIUMPH studies, but it has not been approved by the FDA or any other regulator, and Lilly plans to submit it to the FDA in the first quarter of 2027. A retatrutide dosage chart is therefore a map of someone else's research, not a dosing sheet. The table below compiles the two published programs side by side, as each trial's publication reports its arms.

For the longer argument about why a trial protocol is not a label, and how Lilly built that protocol in the first place, the retatrutide triple-agonist trial history covers that ground directly. This piece stays narrow: it is a retatrutide dosage chart, section by section, sourced from the published trial record. For where every catalog compound stands with regulators, see the regulatory status tracker.

Phase 2 trial arms tested a 2 mg starting dose stepped up every 4 weeks#

The original 2023 obesity trial gave higher-dose arms a retatrutide starting dose of 2 mg or 4 mg before raising it toward a fixed target. Participants assigned to 4 mg or higher began with an initial dose of 2 mg or 4 mg, followed by dose escalation every 4 weeks for up to 12 weeks. The trial randomized 338 adults to one of seven groups: 1 mg, two separate 4 mg groups split by starting dose, two 8 mg groups split by starting dose, a 12 mg group, or placebo.

The choice of retatrutide starting dose mattered almost as much as the final target. The frequency of gastrointestinal adverse events was higher in the 8 mg and 12 mg groups, and higher among participants who began at 4 mg than among those who began at 2 mg, as the trial's own authors noted. At 48 weeks, mean weight change was -8.7% in the 1 mg group, -17.1% in the combined 4 mg group, -22.8% in the combined 8 mg group, and -24.2% in the 12 mg group, compared with -2.1% on placebo.

The Phase 3 program that followed started every arm at the lower 2 mg dose instead of splitting participants across two starting points.

Trial protocol · Phase 3 TRIUMPH titration

Every TRIUMPH-1 arm climbs the same four-week ladder to a different stop

All three retatrutide arms start at 2 mg and add one step every 4 weeks until they reach their assigned target.

Target doses of 4 mg, 9 mg, and 12 mg mark the trial's three maintenance levels#

TRIUMPH-1 fixed its retatrutide maintenance dose at one of three levels: 4 mg, 9 mg, or 12 mg once weekly. The Phase 3 trial randomized 2,339 adults with obesity or overweight, without diabetes, in a 1:1:1:1 ratio to retatrutide 4 mg, 9 mg, or 12 mg, or placebo, for 80 weeks. Each retatrutide maintenance dose was reached by the same climbing schedule, not by starting participants directly at their assigned level.

Under the trial's treatment-regimen (intention-to-treat) estimand, the mean percent change in body weight at week 80 was -17.6% on 4 mg, -23.7% on 9 mg, and -25.0% on 12 mg, compared with -3.9% on placebo, with differences versus placebo of -19.8 and -21.0 percentage points for the 9 mg and 12 mg arms. Weight loss has been shown to scale with the assigned maintenance dose at every level tested, and the gap against placebo widens as the target climbs.

Trial evidence · treatment-regimen estimand

TRIUMPH-1's three retatrutide doses each beat placebo by a wide margin

Mean percent change in body weight at week 80, treatment-regimen (intention-to-treat) estimand.

TRIUMPH-1's primary weight comparisons were the 9 mg and 12 mg arms against placebo, and both were met (P < 0.001). The 4 mg arm, which has a single escalation step, also lost far more weight than placebo.

Retatrutide titration schedules follow the trial's four-week steps#

A retatrutide titration schedule that follows the trial record starts at 2 mg, holds for four weeks, then steps through 4 mg, 6 mg and 9 mg toward 12 mg, stopping at whichever target is being tracked. Klarovel's engine uses exactly this ladder for retatrutide, labelled investigational at every step.

Following the trial pace removes a layer of guesswork: the published record already set the step size and the interval, so there is no reason to improvise one. To turn a milligram dose into syringe units for a given vial, the retatrutide calculator does the arithmetic.

It is worth separating two things that often get merged in casual descriptions: the Phase 2 trial's ladder (1, 4, 8, 12 mg targets, starting at 2 or 4 mg) and the Phase 3 ladder (4, 9, 12 mg targets, starting only at 2 mg). A retatrutide titration schedule copied from one trial without noting which one can misstate both the starting point and the intermediate steps. Reading the trial publication, not a secondhand summary, is the way to confirm which ladder a given reference is describing.

Weekly subcutaneous injection timing follows the same pattern across every studied dose#

Every retatrutide arm across both trial generations used the same injection mechanics: once weekly, under the skin, regardless of dose level. TRIUMPH-1 describes a once-weekly subcutaneous injection of retatrutide at a dose of 4 mg, 9 mg, or 12 mg, with no arm tested on a different injection frequency. Research suggests that consistency follows from the compound's pharmacokinetics: a half-life of roughly six days supports weekly dosing without the peaks and troughs a shorter-acting molecule would produce.

A retatrutide injection schedule, in every published trial, is a single weekly event rather than a split or daily regimen. This held at the lowest dose tested and at the highest. The retatrutide injection schedule did not change shape as participants moved up the titration ladder, only the amount injected at that weekly interval changed.

Consistency in timing does not mean consistency in tolerability. The next section covers how side effects moved as the dose climbed, even though the injection pattern itself stayed fixed.

Higher target doses correlate with more reported gastrointestinal side effects in the trial data#

Retatrutide side effects by dose followed a clear upward pattern in TRIUMPH-1, concentrated in the gastrointestinal system. Lilly's topline results report nausea in 28.6% of the 4 mg group, 38.4% of the 9 mg group, and 42.4% of the 12 mg group, against 14.8% on placebo. Vomiting rose from 10.6% to 22.8% and 25.3% (4.8% on placebo), diarrhea was 25.2%, 34.1% and 32.0% (13.5%), and constipation 23.8%, 25.9% and 26.1% (10.9%). Dysesthesia, an abnormal skin sensation, was reported in 5.1%, 12.3% and 12.5%, against 0.9% on placebo.

Trial evidence · adverse-event reporting

Nausea climbs with each higher retatrutide target dose

Share of TRIUMPH-1 participants reporting nausea at each assigned maintenance dose.

Discontinuation for an adverse event also rose with dose: 4.1% on 4 mg, 6.9% on 9 mg and 11.3% on 12 mg, against 4.9% on placebo, in the same topline report. Studies have shown a similar dose-related gastrointestinal pattern with other incretin-based therapies, and Lilly describes the adverse-event types as generally consistent with that class.

Retatrutide's studied doses sit above semaglutide's range and inside tirzepatide's#

Retatrutide's trial doses run on a different numeric scale than semaglutide's approved range and overlap much of tirzepatide's injectable range, though its highest studied dose stays below tirzepatide's ceiling. Comparing retatrutide vs tirzepatide dosage side by side only works mg to mg if the reader remembers these are three different molecules with different potency per milligram, not interchangeable units.

Semaglutide's weight-management ceiling, approved as Wegovy, is 2.4 mg once weekly, a dose established in the STEP 1 trial. Tirzepatide's approved ceiling, as Zepbound, is 15 mg once weekly, reached through 2.5 mg steps starting from a 2.5 mg initiation dose. Retatrutide's trial ladder runs from a 2 mg start to a 12 mg ceiling, whole-milligram numbers from the first injection onward, a scale that sits well above semaglutide's fractional-milligram range and inside the same general order of magnitude as tirzepatide's.

A retatrutide vs tirzepatide dosage comparison on efficacy alone misses the regulatory gap between them. Tirzepatide has an FDA label; retatrutide does not. For a fuller head-to-head on mechanism and trial outcomes, tirzepatide versus retatrutide and semaglutide versus retatrutide both go deeper than dose numbers alone. Readers who want tirzepatide's own reference chart in the same format this piece uses for retatrutide can find it in the tirzepatide complete guide.

A retatrutide dosage chart is a research reference, not a prescription#

The honest version of a retatrutide dosage chart is the one printed above: trial arms, trial weeks, trial outcomes, nothing more. Retatrutide remains investigational, and every number tied to it, from the 2 mg start to the 12 mg ceiling, belongs to a study protocol rather than a label. Klarovel sells no peptides. It builds a personalized protocol from your health data, checked by the engine's safety rules, for $99 one time. To go further, use the retatrutide calculator, read how Klarovel works, or create an account.