Retatrutide Dosage Chart: Doses, Units & Titration

Community-reported protocols start at 0.25–0.5 mg/week and titrate to 1.5–4 mg/week over 8–12 weeks as GI tolerance is assessed. Phase 2 trials used up to 12 mg/week and produced 24.2% body weight loss at 48 weeks — community protocols are deliberately more conservative.

Research-context information only. Retatrutide is an investigational drug not approved by the FDA. Protocols, doses, and reactions reported below come from published clinical trials and self-reported community sources. This article reports what has been documented, not what should be done. Possession or use of investigational drugs outside an authorized clinical trial may be illegal in your jurisdiction. Consult a licensed physician for personal medical decisions.

Retatrutide is a triple-agonist peptide targeting GLP-1 + GIP + glucagon receptors simultaneously — the most pronounced weight-loss data from any metabolic peptide studied to date. Below: the community-reported 8-weeks-on/8-weeks-off cycle, week-by-week titration math, side-effect-driven adjustments, and how community doses compare to the trial-published 12 mg/week ceiling.

What Phase 3 Trials Used

Lilly's Phase 3 TRIUMPH program dosed retatrutide once weekly by subcutaneous injection. Per Lilly's trial releases, participants started at 2 mg once weekly and stepped up every four weeks until reaching an assigned target dose: 4 mg (after one 4-week step at 2 mg), 9 mg (via steps at 2, 4 and 6 mg) or 12 mg (via steps at 2, 4, 6 and 9 mg). On that schedule, the 12 mg arm reached its target dose at week 16 (Lilly TRIUMPH-1 release, May 2026).

Results in the table are the efficacy-estimand figures from Lilly's topline releases (TRIUMPH-2 and TRIUMPH-3 release, July 2026). The peer-reviewed papers report the more conservative treatment-regimen estimand: TRIUMPH-1 in the New England Journal of Medicine reported 17.6–25.0% mean weight reduction versus 3.9% on placebo (NEJM, 2026), and TRIUMPH-2 in The Lancet reported −11.9%, −16.8% and −18.8% versus −5.1% (Lancet, 2026). In TRIUMPH-1, Lilly reported discontinuation due to adverse events of 4.1%, 6.9% and 11.3% across the 4, 9 and 12 mg arms, versus 4.9% on placebo.

How Phase 2 differed: the 48-week Phase 2 obesity trial (338 adults) tested 1, 4, 8 and 12 mg weekly arms, some started at 2 mg and some at 4 mg; investigators reported that gastrointestinal events were partially mitigated by the lower 2 mg starting dose (Jastreboff et al., 2023). Phase 3 used a 2 mg start for every arm and replaced the 8 mg target with 9 mg.

Retatrutide remains an investigational drug and is not FDA-approved for any indication. The community-reported protocol below uses smaller, split doses and differs from every trial schedule above. For full trial readouts and safety data, see Retatrutide Phase 3 Results.

Quick Reference: Community-Reported Protocol

Community-reported protocol (self-reported; compiled from community dosing logs and reconstitution guides — documentation of what sources describe, not a recommendation):

Self-reported starting doses are typically 0.25 mg for the first week to assess GI tolerance, before increasing to 0.5 mg.

Cycling Details

The most commonly reported community cycle is 0.5 mg 3x/week (1.5 mg/week total) for 8 weeks, then 8 weeks off. Some community reports describe goal-oriented cycles — continuing until a target weight, then cycling off — and maintenance phases reported at 2x/week (1 mg/week total). Clinical trials did not cycle: Phase 2 and Phase 3 participants dosed once weekly throughout.

The 3x/week split (vs. single weekly injection used in clinical trials) may provide more stable receptor activation throughout the week.

Routes of Administration

Subcutaneous injection is the only route. Retatrutide cannot be taken orally.

• Sites: Abdomen, thigh, or anywhere with subcutaneous fat
• Volume: 0.1 mL with insulin syringe (29-31 gauge)
• Rotation: Trial protocols describe rotating injection sites to minimize lipodystrophy risk

Reconstitution Quick Reference

Math: 10 mg / 2 mL = 5 mg/mL. For 0.5 mg: 0.5 / 5 = 0.1 mL = 10 units.

Community protocols describe gentle swirling — not shaking — to avoid degradation, with storage at 2–8°C and use within 28 days of reconstitution. For step-by-step instructions and vial size comparisons, see the full Retatrutide Reconstitution Guide.

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Where These Numbers Come From

Community doses represent a conservative approach compared to clinical trials.

Phase 2 obesity trial: 338 adults were randomized to placebo or to separate retatrutide dose groups with target doses of 1, 4, 8 or 12 mg once weekly for 48 weeks. Each participant stayed in one group; the trial did not titrate a single cohort from 1 mg to 12 mg. The 4 mg and 8 mg targets were each tested with a 2 mg and a 4 mg initial dose, and the 12 mg group started at 2 mg and escalated to its target. Mean weight loss at 48 weeks reached 24.2% in the 12 mg group (Jastreboff et al., 2023).

Phase 2 diabetes trial: Dose-dependent HbA1c reductions — minimum effective dose for meaningful glucose control was 4 mg/week (Rosenstock et al., 2023). Community protocols at 1.5 mg/week fall below this threshold.

Why community doses are lower: No FDA approval means conservative self-titration. Lower doses reduce GI side effects. The lowest Phase 2 dose group (1 mg/week) is already close to the community protocol (1.5 mg/week split 3x). Many see significant effects at these lower levels.

Research Vial Sizing

Larger vials offer better per-mg pricing. Compare current vial options and verified vendors at Best Retatrutide Vendors.

Stacking Protocols

Retatrutide already hits three major metabolic pathways, leaving few complementary targets. Adding other GLP-1 agonists (semaglutide, tirzepatide) is redundant and increases side effects. Stacking with other weight loss peptides is generally unnecessary.

Side Effects & Safety

• Nausea — most common (~33% at high doses), dose-dependent, typically improves over time
• GI effects — vomiting, diarrhea, constipation, slowed gastric emptying (GLP-1 class effects)
• Heart rate changes — transient increases observed in trials, peaked at 24 weeks then declined
• Injection site reactions — mild redness or irritation
• Gallbladder risk — rapid weight loss increases gallstone risk (common with any rapid weight loss method)
• No major safety signals in 48-week trial up to 12 mg weekly
• At community doses (1.5 mg/week), side effects are notably milder than high-dose trial groups

Dosage Chart

This dosage chart consolidates the doses reported in published Phase 2 trials and self-reported community protocols, expressed in milligrams (mg) and converted to units on a standard 100-unit / 1mL insulin syringe.

Self-reported titration described in community sources: 0.25 mg 3x/week for week 1, then 0.5 mg 3x/week thereafter, with optional 8-week-on / 8-week-off cycling.

mg to Units Conversion

On a standard 100-unit insulin syringe, each "unit" equals 0.01 mL (so 100 units = 1 mL). Once retatrutide is reconstituted, the conversion from a target mg dose to syringe units depends entirely on the chosen dilution.

The two reconstitution ratios most often described in community protocols are below.

Reconstitution A: 10 mg vial + 2 mL BAC water (5 mg/mL) — the commonly used "20 units = 1 mg" dilution that keeps draws in the practical 5-80 unit range.

Reconstitution B: 10 mg vial + 1 mL BAC water (10 mg/mL) — half the volume per dose, useful when storing small total volumes; mid-range doses still fit on one syringe.

These conversions reflect the dilutions documented in published reconstitution protocols and self-reported community sources. They are reporting how reconstitution math is described, not a recommended dosing schedule.