Retatrutide GLP-3 RT (40 mg Vial) Dosage Protocol
Retatrutide is a triple-receptor agonist (GLP-1 / GIP / glucagon) studied in Phase 2 trials for body-weight reduction up to 24% at 48 weeks. It is among the most potent incretin compounds in clinical investigation. This page covers the 40 mg vial.
⚡ Quickstart Highlights
Dosing & Reconstitution Guide
Phase 2 and phase 3 Retatrutide schedules converted for a 40 mg vial reconstituted to 2 mL (20 mg/mL)
Phase 2 Trial Schedule (2 mL = 20 mg/mL)
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 10 units | 0.1 mL |
| Weeks 5 to 8 | 4 mg | 20 units | 0.2 mL |
| Weeks 9 to 12 | 8 mg | 40 units | 0.4 mL |
| Weeks 13+ | 12 mg | 60 units | 0.6 mL |
Frequency: Once weekly by subcutaneous administration. This table shows the lower-start 12 mg arm from the 48-week phase 2 obesity trial. The study also evaluated separate 1 mg, 4 mg, and 8 mg target arms. Every listed amount fits within one 1 mL syringe at this concentration.
Phase 3 Trial Schedule (2 mL = 20 mg/mL)
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 10 units | 0.1 mL |
| Weeks 5 to 8 | 4 mg | 20 units | 0.2 mL |
| Weeks 9 to 12 | 6 mg | 30 units | 0.3 mL |
| Weeks 13 to 16 | 9 mg | 45 units | 0.45 mL |
| Weeks 17+ | 12 mg | 60 units | 0.6 mL |
Frequency: Once weekly by subcutaneous administration. The phase 3 program began at 2 mg and increased every four weeks until the assigned 4 mg, 9 mg, or 12 mg target was reached. Every listed amount fits within one 1 mL syringe at this concentration.
Reconstitution Steps
- Clean the vial stopper and gather the sterile supplies required by the research procedure.
- Add 2 mL bacteriostatic water slowly down the vial wall.
- Gently swirl or roll until dissolved. Do not shake.
- Label the vial 20 mg/mL with the preparation date and follow the documented refrigerated storage period.
The weekly amounts remain identical across the Retatrutide family. The 40 mg vial changes only the concentration, U-100 units, volume, and supply calculations.
Supplies Needed
Straightforward 12-week and 24-week planning for a 40 mg vial at 20 mg/mL.
| Item | Phase 2, 12 weeks | Phase 2, 24 weeks | Phase 3, 12 weeks | Phase 3, 24 weeks |
|---|---|---|---|---|
| Retatrutide vials (40 mg each) | Minimum 2 vials (56 mg required). | Minimum 5 vials (200 mg required). | Minimum 2 vials (48 mg required). | Minimum 5 vials (180 mg required). |
| U-100 insulin syringes (1 mL capacity) | 12 new syringes. | 24 new syringes. | 12 new syringes. | 24 new syringes. |
| Bacteriostatic water (10 mL bottles) | 1 bottle by volume (4 mL required). | 1 bottle by volume (10 mL required). | 1 bottle by volume (4 mL required). | 1 bottle by volume (10 mL required). |
| Alcohol swabs | 24 swabs minimum; 1 box of 100 covers the calculation. | 48 swabs minimum; 1 box of 100 covers the calculation. | 24 swabs minimum; 1 box of 100 covers the calculation. | 48 swabs minimum; 1 box of 100 covers the calculation. |
Sharps disposal: One appropriately sized container for used syringes.
Stability planning: Vial and diluent totals are minimum arithmetic quantities. Follow the exact product documentation for sterility, storage, handling loss, and discard timing.
Protocol Overview
Retatrutide is positioned at the high end of the incretin landscape. The compound has no validated "aggressive" or accelerated path — every clinical trial uses the same paced ramp. After cessation, weight regain is the norm without lifestyle anchoring (protein, resistance training, sustainable caloric intake).
Storage Instructions
| State | Temperature | Duration |
|---|---|---|
| Lyophilized | −20°C (−4°F) | Up to 24 months, dry & dark |
| Reconstituted | 2–8°C (35–46°F) | Up to 28 days, protect from light |
Important Notes
How This Works
Retatrutide simultaneously activates GLP-1, GIP, and glucagon receptors — the only triple-agonist in clinical trials. GLP-1 activation slows gastric emptying and enhances satiety. GIP augments insulin secretion in response to glucose and modulates lipid metabolism. The glucagon-receptor component drives an increase in energy expenditure absent from dual or single agonists.
The molecule is fatty-acid acylated to bind albumin in serum, slowing renal clearance and enabling once-weekly dosing. The combined three-receptor profile produces greater body-weight reduction in trials than any prior incretin compound.
Potential Benefits & Side Effects
Potential Benefits
- Phase 2 obesity trial: up to 24% weight reduction at 48 weeks (8 mg).
- Phase 2 type-2 diabetes: HbA1c reductions up to 2.0% with substantial weight loss.
- Triple receptor activation drives both appetite suppression and increased energy expenditure.
- Improvements in lipid profile and liver fat content reported alongside weight loss.
Side Effect Profile
- Nausea (most common, dose-dependent — typically resolves with the 4-week titration hold).
- Vomiting and diarrhea, particularly during titration steps.
- Decreased appetite (target effect; can become limiting at higher doses).
- Fatigue and headaches reported during early weeks.
- Heart-rate elevation observed in some trial participants.
Lifestyle Factors
- Hydrate aggressively — incretin agonists slow gastric emptying and reduce thirst signaling.
- Prioritize protein (1.0–1.6 g/kg/day) to preserve lean mass during rapid weight loss.
- Resistance training 2–3×/week is critical to maintain muscle.
- Limit high-fat meals immediately after dosing — fatty foods amplify nausea.
- Smaller, more frequent meals are better tolerated than large meals.
- Sleep 7–9 hours/night — sleep loss blunts GLP-1 efficacy on appetite.
Injection Technique
- Inject subcutaneously into abdomen (avoid 2-inch radius around navel), outer thigh, or upper arm.
- Rotate injection sites every dose to prevent lipohypertrophy.
- 90° angle with short (4–8 mm) insulin syringes.
- Bring vial to room temperature 15 min before injecting.
- Hold 5 seconds after full plunger depression before withdrawing.