Retatrutide dosing: TRIUMPH-1 Phase 3 protocol starts all arms at 2mg once weekly, escalating every 4 weeks: 2mg → 4mg → 9mg → 12mg. Half-life is ~144 hours (6 days). Titration to maintenance in 12 weeks — faster than tirzepatide or semaglutide.
TRIUMPH-1 Protocol · Updated May 21, 2026
Retatrutide dosing
& titration.
Phase 3 protocol.
TRIUMPH-1 step schedule, half-life data, reconstitution guide, and dose-response outcomes. Research reference only — not medical advice.
2mgTRIUMPH-1 starting dose
12 wksTo 12mg maintenance
~144hApproximate half-life
4 wksMinimum per step
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TRIUMPH-1 Phase 3 Protocol
The titration schedule.
Step by step.
All three TRIUMPH-1 dose arms (4mg, 9mg, 12mg) started at 2mg and escalated every 4 weeks. The 4mg arm stops after one step.
Weeks 1–4
2
mg · once weekly
Starting dose for all arms. GLP-1 receptor activation begins. GI side effects most common as the body adjusts to incretin signaling.
Weeks 5–8
4
mg · once weekly
4mg arm maintenance stop. Largest relative increase (2×). GI AEs may peak here. 4mg arm: 19.0% weight loss at 80 wks · 4.1% discontinuation.
Weeks 9–12
9
mg · once weekly
9mg arm maintenance stop. Full incretin effects established. Glucagon activation intensifies. 9mg: 25.9% at 80 wks · only 8.8% dysesthesia.
Week 13+
12
mg · maintenance
Maximum studied dose. 28.3% at 80 wks · 30.3% at 104 wks. Highest dysesthesia (20.9%) — 9mg may be preferred for tolerability.
Source: TRIUMPH-1 (NCT05929066, n=2,339, Eli Lilly May 21 2026) · Phase 2: Jastreboff et al. NEJM 2023 used 1mg start and 1→2→4→8→12mg steps. Research reference only.
Phase 3 Dose-Response
What each dose
produced at 80 weeks.
TRIUMPH-1 ran three clean dose arms. More efficacy at higher doses — but tolerability tradeoffs are real and documented.
0%
Weight loss · 12mg · 80 weeks
70.3 lbs · 45.3% reached ≥30% loss · 11.3% DC rate
0%
Weight loss · 9mg · 80 weeks
64.4 lbs · 8.8% dysesthesia · 6.9% DC rate · Best tolerability/efficacy balance
0%
Weight loss · 4mg · 80 weeks
47.2 lbs · 4.1% DC (lower than placebo) · Single escalation step
0%
Weight loss · 12mg · 104 weeks (BMI ≥35 extension)
85.0 lbs · Surgical-level threshold · Continued loss without plateau
Dose Comparison
Efficacy vs tolerability.
All three arms.
| Dose | Weight Loss % (80 wks) | Avg lbs lost | ≥30% weight loss | Discontinuation | Dysesthesia |
|---|---|---|---|---|---|
| 12mg | 28.3% | 70.3 lbs | 45.3% | 11.3% | 20.9% |
| 9mg | 25.9% | 64.4 lbs | ~35% | 6.9% | 8.8% |
| 4mg | 19.0% | 47.2 lbs | ~14% | 4.1% | ~3% |
| Placebo | 3.9% | ~9 lbs | — | 4.9% | — |
Research note — 9mg vs 12mg: TRIUMPH-1 data shows 9mg achieved 25.9% weight loss with 8.8% dysesthesia, vs 12mg at 28.3% with 20.9% dysesthesia. The 9mg dose achieves ~91% of 12mg efficacy with less than half the neurological side effect rate — a meaningful tradeoff for research protocol design where compliance is a variable.
Source: TRIUMPH-1, Eli Lilly May 21 2026, NCT05929066. Dysesthesia = abnormal skin sensations, typically mild and transient. DC = treatment discontinuation.
Pharmacokinetics
Half-life &
reconstitution guide.
Understanding PK is essential for research protocol design and dosing interval decisions.
⏱ Half-Life & Dosing Rationale
Day 0
Day 6
Day 12
Day 18
Day 24
Day 30
Day 36
- t½~144 hour half-life (6 days)Supports once-weekly subcutaneous administration. Steady state at each dose level is reached within 4–5 weeks — the pharmacokinetic basis for 4-week titration steps.
- 1×Once-weekly injection, same day each weekConsistent day-of-week administration maintains stable plasma trough levels and reduces inter-dose variability.
- 12w12 weeks to maintenance (vs 16–20 wks tirzepatide)Retatrutide reaches maintenance dose faster than tirzepatide or semaglutide due to its Phase 3 protocol design.
🧪 Reconstitution Protocol
- 1Allow vial to reach room temperatureRemove from freezer 15–20 minutes before reconstitution. Do not use warm water or microwave.
- 2Inject bacteriostatic water down the vial wallDo not inject directly onto lyophilized powder cake. Side-wall delivery prevents denaturation.
- 3Swirl gently — do not shakeShaking generates bubbles and can degrade peptide bonds. Swirl until fully dissolved. Solution should be clear.
- 4Store at 2–8°C, use within 28 daysProtect from light. Do not freeze reconstituted solution. Lyophilized vials: −20°C long-term or 2–8°C short-term.
Available Now
GLP-3 RT — Retatrutide research analog.
In Stock · Ships Today
In Stock · Ships Today
GLP-3 RT
Retatrutide Analog · Triple GIP/GLP-1/GCG Receptor Agonist · COA-Verified
- ✓ Triple receptor activity — GIP, GLP-1 & glucagon
- ✓ 15mg and 30mg vials available
- ✓ COA-verified 99%+ purity by independent lab
- ✓ Lyophilized powder, research grade
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- ✓ Free shipping on orders over $100
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Research Context
Retatrutide program overview.
2mg
Phase 3 starting dose
TRIUMPH-1 updated from Phase 2's 1mg start to 2mg. All three arms (4/9/12mg) begin at 2mg and escalate every 4 weeks before reaching their maintenance dose.
TRIUMPH-1, Eli Lilly · May 2026
n=2,339
TRIUMPH-1 participants
The largest retatrutide Phase 3 trial to date. Adults with obesity or overweight and at least one weight-related comorbidity, without diabetes. 80-week primary endpoint.
NCT05929066 · May 21 2026
~2027
Projected FDA approval
NDA submission anticipated late 2026 following additional Phase 3 readouts. Standard FDA review is 10–12 months. GLP-3 RT remains available for research throughout.
Analyst consensus · May 2026
FAQ
Retatrutide dosing questions.
TRIUMPH-1 Phase 3 starts all arms at 2mg once weekly subcutaneous injection. This differs from the Phase 2 protocol (Jastreboff et al., NEJM 2023) which began at 1mg. The 2mg start was adopted in Phase 3 to simplify the escalation schedule — from 1→2→4→8→12mg (Phase 2) to 2→4→9→12mg (Phase 3).
Retatrutide simultaneously activates three receptor systems (GLP-1, GIP, glucagon). Rapid dose increases before receptor adaptation causes pronounced GI adverse events. The 4-week minimum per step aligns with retatrutide's ~144-hour half-life — allowing plasma levels to reach steady state (4–5 weeks) before the next increase. The 4mg step (doubling from 2mg) is where GI side effects are most commonly reported as the largest relative increase in the schedule.
TRIUMPH-1 data shows a meaningful tolerability advantage at 9mg: 25.9% weight loss with 8.8% dysesthesia and 6.9% discontinuation vs 12mg at 28.3% with 20.9% dysesthesia and 11.3% discontinuation. The 9mg dose achieves ~91% of 12mg efficacy with less than half the neurological side effect rate. For research protocols where subject compliance is a primary consideration, 9mg may represent the optimal maintenance dose. Protocol design should be driven by specific research objectives.
Retatrutide has an approximate half-life of 144 hours (~6 days), supporting once-weekly subcutaneous administration. With once-weekly dosing, steady-state plasma concentration is reached within 4–5 weeks at any given dose level. This is the pharmacokinetic basis for the 4-week hold per titration step — each step must reach steady state before tolerability can be reliably assessed. The consistent once-weekly same-day injection schedule minimizes inter-dose plasma variability.
Standard protocol: allow vial to reach room temperature (15–20 min). Inject bacteriostatic water slowly down the inner vial wall — not directly onto the lyophilized powder. Swirl gently until dissolved — do not shake. Common concentrations: 1.5mL BAC water per 15mg vial = 10mg/mL. Store reconstituted at 2–8°C, protected from light, use within 28 days. Do not freeze reconstituted peptide. Lyophilized GLP-3 RT from Evo Peptides: −20°C long-term storage.
Evo Peptides supplies GLP-3 RT — a retatrutide analog for laboratory and in-vitro research. COA-verified at 99%+ purity by an independent third-party laboratory. Available in 15mg ($89.95) and 30mg ($129.95) lyophilized powder vials. Same-day shipping before 3PM CST from Wisconsin. For research use only — not for human consumption. Order at evopeptidesus.com →
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COA-verified retatrutide analog. Same-day shipping before 3PM CST from Wisconsin. Free shipping on orders over $100.
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For Research Use Only. GLP-3 RT is sold exclusively for laboratory and in-vitro research. Not for human or veterinary consumption, diagnosis, treatment, or prevention of any disease. All dosing data from published Eli Lilly Phase 2 and Phase 3 clinical trial protocols (TRIUMPH-1, NCT05929066; Jastreboff et al. NEJM 2023). Evo Peptides is not affiliated with Eli Lilly. Not medical advice. © 2026 Evo Peptides · Wisconsin, USA.