Retatrutide Dosage Chart
Retatrutide Dosage calculations for a 50 mg vial use the same once-weekly amounts studied in human clinical trials. Adding 2.5 mL of bacteriostatic water produces 20 mg/mL, so each U-100 unit contains 200 mcg.
- Reconstitute: Add 2.5 mL of bacteriostatic water to produce 20 mg/mL.
- Research frequency: Once weekly by subcutaneous administration in the cited human trials.[1][3][5]
- Weekly research range: The cited programs evaluated target amounts through 12 mg weekly.[1][2][3]
- Easy measuring: 1 U-100 unit = 0.01 mL = 200 mcg.
- Vial size: The 50 mg label is total nominal vial content, not a weekly amount.
- Vial coverage: At the 2 mg research stage, one vial supplies 25 full weekly amounts. At the 12 mg research stage, one vial supplies 4 full weekly amounts with 2 mg remaining. These are mass calculations, not vial storage or discard periods.
Research context: For mechanisms, human and preclinical research, limitations, and safety context, read the Retatrutide Peptide research overview.
Dosing & Reconstitution Guide
The same phase 2 and phase 3 schedules converted for a 50 mg vial
Phase 2 Trial Schedule (2.5 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.[1] Every listed amount fits within one 1 mL syringe at this concentration.
Phase 3 Trial Schedule (2.5 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.[2][3] 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 2.5 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.
Supplies Needed
Straightforward 12-week and 24-week planning for a 50 mg vial at 20 mg/mL.
- Retatrutide vials (50 mg each):
- Phase 2, 12 weeks: Minimum 2 vials (56 mg required).
- Phase 2, 24 weeks: Minimum 4 vials (200 mg required).
- Phase 3, 12 weeks: Minimum 1 vial (48 mg required).
- Phase 3, 24 weeks: Minimum 4 vials (180 mg required).
- U-100 insulin syringes (1 mL capacity):
- Phase 2, 12 weeks: 12 new syringes.
- Phase 2, 24 weeks: 24 new syringes.
- Phase 3, 12 weeks: 12 new syringes.
- Phase 3, 24 weeks: 24 new syringes.
- Bacteriostatic water (10 mL bottles):
- Phase 2, 12 weeks: 1 bottle by volume (5 mL required).
- Phase 2, 24 weeks: 1 bottle by volume (10 mL required).
- Phase 3, 12 weeks: 1 bottle by volume (2.5 mL required).
- Phase 3, 24 weeks: 1 bottle by volume (10 mL required).
- Alcohol swabs:
- Phase 2, 12 weeks: 24 swabs minimum; 1 box of 100 covers the calculation.
- Phase 2, 24 weeks: 48 swabs minimum; 1 box of 100 covers the calculation.
- Phase 3, 12 weeks: 24 swabs minimum; 1 box of 100 covers the calculation.
- Phase 3, 24 weeks: 48 swabs minimum; 1 box of 100 covers the calculation.
- Sharps container: 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
Quick reference for the shared Retatrutide research schedules.
- Route: Subcutaneous administration in the cited trials.[1][3][5]
- Frequency: Once weekly.
- Research targets: Phase 2 studied 1 mg, 4 mg, 8 mg, and 12 mg groups; phase 3 studied 4 mg, 9 mg, and 12 mg targets.[1][2][3]
- Concentration: 50 mg divided by 2.5 mL equals 20 mg/mL.
- Unit conversion: 1 U-100 unit equals 200 mcg.
Dosing Protocol
The tables keep the phase 2 and phase 3 schedules separate.
- Phase 2 lower-start 12 mg arm: 2 mg, 4 mg, 8 mg, then 12 mg in four-week steps.[1]
- Phase 3 12 mg target: 2 mg, 4 mg, 6 mg, 9 mg, then 12 mg in four-week steps.[2][3]
- Frequency: Once weekly by the subcutaneous route.
- Measurement: Use the units and mL displayed beside each weekly amount.
- Consistency: Vial size does not change the weekly research schedule.
Storage Instructions
Use the storage directions for the exact supplied formulation.
- Before preparation: Keep the vial dry, protected from light, and stored according to its documentation.[16]
- After preparation: Refrigerate only as permitted by the exact formulation and diluent instructions.
- Labeling: Record the concentration, preparation date, storage conditions, and documented discard date.
- Handling: Avoid unnecessary agitation and repeated freeze-thaw cycles.[16][17]
Important Notes
Practical details for reading the schedules and calculations correctly.
- The weekly amounts remain the same across every Retatrutide vial size. Only the vial concentration, U-100 units, volume, and supply totals change.
- The phase 2 and phase 3 tables represent separate research schedules and should not be combined into one progression.[1][2][3]
- Use a new sterile syringe for each injection and place used sharps in an appropriate container.[14][15]
- Rotate subcutaneous sites according to the governing research procedure.[13][14][15]
- Record the weekly amount, calculated units, volume, date, and administration site consistently.
How This Works
Retatrutide activates GIP, GLP-1, and glucagon receptors. This combined receptor activity was studied using once-weekly subcutaneous schedules in controlled human trials.[1][3][4][5]
Clinical Benefits
Results below summarize observations from controlled human research.
- The phase 2 obesity trial reported dose-related body-weight reductions across the studied target groups through 48 weeks.[1]
- The phase 2 diabetes trial reported reductions in glycated hemoglobin and body weight across studied retatrutide groups.[5]
- TRANSCEND-T2D-1 reported improvements in glycated hemoglobin and body weight at 40 weeks in adults with type 2 diabetes.[3]
- Cardiometabolic measurements were evaluated as secondary outcomes in the clinical research programs.[1][3][5][10]
Side Effects
Safety findings remain specific to the studied populations, products, schedules, and monitoring plans.
- Gastrointestinal events, including nausea, diarrhea, vomiting, and constipation, were among the most commonly reported events.[1][3][5][12]
- Events were more frequent during dose escalation and were generally mild to moderate in the phase 2 obesity study.[1]
- A lower 2 mg starting amount improved gastrointestinal tolerability compared with a 4 mg start in the phase 2 obesity trial.[1]
- Dose-dependent heart-rate increases were observed in phase 2 research and declined after peaking during follow-up.[1]
Lifestyle Factors
Consistent study conditions make weekly observations easier to interpret.
- Record diet, physical activity, sleep, hydration, and gastrointestinal symptoms consistently.
- Use the same body-weight, waist, glucose, and laboratory measurement methods throughout the observation period.
- Compare results within the same population, dose arm, follow-up period, and analysis plan.
Injection Technique
General subcutaneous research technique should follow the approved institutional or laboratory procedure.[13][14][15]
- Use a new sterile syringe and needle for every injection and each separate vial entry.
- Clean the vial stopper and selected site, then allow the surface to dry.
- Use the needle length, angle, and skinfold method specified by the governing procedure.
- Rotate sites systematically and document each administration.
- Place used sharps immediately in an appropriate sharps container.
Important Research Note
This page summarizes published human research schedules and the corresponding arithmetic for a 50 mg vial. It is educational information and not individualized medical advice.
References
- New England Journal of Medicine (2023): Triple-Hormone-Receptor Agonist Retatrutide for Obesity: randomized phase 2 trial
- Eli Lilly and Company (2026): Phase 3 target doses and four-week escalation schedule
- The Lancet (2026): TRANSCEND-T2D-1 randomized phase 3 retatrutide trial
- Cell Metabolism (2022): Discovery and translational pharmacology of LY3437943
- The Lancet (2023): Retatrutide for type 2 diabetes: randomized phase 2 trial
- ClinicalTrials.gov: Phase 2 retatrutide obesity study NCT04881760
- Current Obesity Reports (2025): Triple agonism-based therapies for obesity
- Nature Reviews Endocrinology (2024): Multi-receptor agonists for metabolic disease
- Diabetes Care (2024): Incretin-based therapies and cardiovascular considerations
- New England Journal of Medicine (2023): Supplementary material for the phase 2 obesity trial
- Hepatology (2024): Triple agonism and hepatic steatosis research
- The Lancet (2023): Supplementary data for the phase 2 diabetes trial
- CDC: Subcutaneous administration guidance
- Johns Hopkins Arthritis Center: How to give a subcutaneous injection
- NCBI Bookshelf: Best practices for injections and related procedures
- GenScript Peptide Services: Peptide storage and handling guidelines
- Journal of Pharmaceutical Sciences (2018): Stability considerations during freeze-thaw cycles