Retatrutide Dosage & Reconstitution Guide
Titration schedule 2 mg → 12 mg, reconstitution math, syringe draw reference — everything in one place.
What Is Retatrutide?
Retatrutide (LY3437943) is a triple GLP-1, GIP, and glucagon receptor agonist developed by Eli Lilly. It has progressed through Phase 3 trials (Eli Lilly's TRIUMPH program). The first Phase 3 readout, TRIUMPH-4 (obesity with knee osteoarthritis, reported December 2025), showed an average 28.7% body weight reduction at 68 weeks on the 12 mg dose. Additional Phase 3 trials — including TRIUMPH-1 (general obesity) and TRANSCEND-T2D-1 (type 2 diabetes) — have reported through 2026, with several more results expected before year-end. Retatrutide remains investigational and is not FDA-approved; an NDA submission is anticipated in late 2026 or early 2027.
Important note: Retatrutide is not FDA-approved and has no brand name equivalent available by prescription. It is available only as a research chemical. Do not combine with semaglutide, tirzepatide, or any other GLP-1 receptor agonist.
Retatrutide vs Tirzepatide vs Semaglutide
Triple vs Dual vs Single Agonist
| Parameter | Retatrutide | Tirzepatide | Semaglutide |
|---|---|---|---|
| Receptors targeted | GLP-1 + GIP + Glucagon | GLP-1 + GIP | GLP-1 only |
| FDA approval status | Not approved (Phase 3) | Approved | Approved |
| Starting dose | 2 mg | 2.5 mg | 0.25 mg |
| Maximum studied dose | 12 mg | 15 mg | 2.4 mg |
| Injection frequency | Once weekly | Once weekly | Once weekly |
| Phase 3 weight reduction | Up to 28.7% at 68 weeks (TRIUMPH-4) | Up to 22.5% at 72 weeks | ~15% at 68 weeks |
Titration Schedule
Standard Retatrutide Titration Protocol
Retatrutide requires slow, structured titration. Gastrointestinal side effects are most common in the first 4–8 weeks and during each dose increase. Slower titration is generally better tolerated.
| Week | Dose | Frequency | Notes |
|---|---|---|---|
| Weeks 1–4 | 2 mg | Once weekly | Starting dose. Expect mild nausea days 1–2. |
| Weeks 5–8 | 4 mg | Once weekly | Advance only if 2 mg well tolerated. |
| Weeks 9–12 | 6 mg | Once weekly | GI effects typically stabilize here. |
| Weeks 13–16 | 8 mg | Once weekly | High-end dose. Monitor closely. |
| Weeks 17–20 | 10 mg | Once weekly | Near maximum studied dose. |
| Weeks 21+ | 12 mg | Once weekly | Highest dose studied in Phase 2 trials. |
Do not advance the dose if nausea is persistent, vomiting occurs more than once in a week, or food intake drops below approximately 800 kcal/day. Hold at the current dose for 4 additional weeks before attempting to advance.
Reconstitution Reference
How Much BAC Water to Add
Retatrutide is used at higher doses than semaglutide. A concentration of 5–10 mg/mL keeps injection volumes manageable at mid to high doses.
| Vial size | BAC water | Concentration | Doses at 2 mg | Doses at 4 mg |
|---|---|---|---|---|
| 5 mg | 1.0 mL | 5.0 mg/mL | 2 | 1 |
| 10 mg | 1.0 mL | 10.0 mg/mL | 5 | 2 |
| 10 mg | 2.0 mL | 5.0 mg/mL | 5 | 2 |
| 20 mg | 2.0 mL | 10.0 mg/mL | 10 | 5 |
| 30 mg | 3.0 mL | 10.0 mg/mL | 15 | 7 |
Compare all peptides on the Peptide Dosage Chart.
Retatrutide Dosage Calculator
Use the calculator to convert 5 mg, 10 mg, 20 mg, or 30 mg retatrutide vials with your BAC water volume into an exact syringe draw. It is especially useful when comparing 5.0 mg/mL and 10.0 mg/mL mixtures across 2–12 mg weekly targets.
Calculate your exact syringe draw
Open the Calculator →Syringe Draw Reference
| Dose | Draw to |
|---|---|
| 2 mg | 40 units |
| 4 mg | 80 units |
| 6 mg | 120 units * |
| 8 mg | 160 units * |
| 10 mg | 200 units * |
| 12 mg | 240 units * |
| Dose | Draw to |
|---|---|
| 2 mg | 20 units |
| 4 mg | 40 units |
| 6 mg | 60 units |
| 8 mg | 80 units |
| 10 mg | 100 units |
| 12 mg | 120 units * |
* Volumes above 100 units (1 mL) require multiple injections. A 10.0 mg/mL concentration is recommended for doses of 4 mg and above — it keeps injections at or below 1 mL up to 10 mg.
Protein intake during retatrutide research
At higher doses (8 mg+), appetite suppression can be significant. Researchers commonly prioritize protein intake — approximately 0.7–1.0 g per pound of lean body mass or target bodyweight — to support muscle preservation during periods of caloric restriction. Protein shakes can help meet targets when appetite is severely reduced.
Supplies Required
| Item | Spec | Notes |
|---|---|---|
| Retatrutide vial | Lyophilized powder | Store at -20°C until use |
| Bacteriostatic water | USP, 0.9% benzyl alcohol | 30 mL multi-dose vial |
| Insulin syringes | U-100, 31g, 0.3–1 mL | Low dead-space preferred |
| Alcohol prep pads | 70% isopropyl, sterile | One per vial entry, one per site |
| Sharps container | Puncture-resistant | Required |
The Retatrutide Protocol Guide
The complete 9-section research protocol — full titration schedule, reconstitution walkthrough, syringe draw reference tables, storage, injection protocol, and the 7 most common mistakes.
$8
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