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Retatrutide Quick Reference (20 mg Vial)
- Vial contents
- 20 mg Retatrutide
- Final volume
- 2 mL
- Concentration
- 10 mg/mL
- One U-100 unit
- 100 mcg in 0.01 mL
Research context: For mechanisms, human and preclinical research, limitations, and safety context, read the Retatrutide Peptide research overview.
Retatrutide Dosage Chart (20 mg Vial)
The same phase 2 and phase 3 schedules converted for a 20 mg vial
Phase 2 Trial Schedule (2 mL = 10 mg/mL)
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 20 units | 0.2 mL |
| Weeks 5 to 8 | 4 mg | 40 units | 0.4 mL |
| Weeks 9 to 12 | 8 mg | 80 units | 0.8 mL |
| Weeks 13+ | 12 mg | 120 units | 1.2 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] Rows above 100 units exceed the capacity of one 1 mL syringe, so the supply calculation counts the required number of syringes.
Phase 3 Trial Schedule (2 mL = 10 mg/mL)
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 20 units | 0.2 mL |
| Weeks 5 to 8 | 4 mg | 40 units | 0.4 mL |
| Weeks 9 to 12 | 6 mg | 60 units | 0.6 mL |
| Weeks 13 to 16 | 9 mg | 90 units | 0.9 mL |
| Weeks 17+ | 12 mg | 120 units | 1.2 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] Rows above 100 units exceed the capacity of one 1 mL syringe, so the supply calculation counts the required number of syringes.
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 10 mg/mL with the preparation date and follow the documented refrigerated storage period.
Supplies Needed
Straightforward 12-week and 24-week planning for a 20 mg vial at 10 mg/mL.
- Retatrutide vials (20 mg each):
- Phase 2, 12 weeks: Minimum 3 vials (56 mg required).
- Phase 2, 24 weeks: Minimum 10 vials (200 mg required).
- Phase 3, 12 weeks: Minimum 3 vials (48 mg required).
- Phase 3, 24 weeks: Minimum 9 vials (180 mg required).
- U-100 insulin syringes (1 mL capacity):
- Phase 2, 12 weeks: 12 new syringes.
- Phase 2, 24 weeks: 36 new syringes.
- Phase 3, 12 weeks: 12 new syringes.
- Phase 3, 24 weeks: 32 new syringes.
- Bacteriostatic water (10 mL bottles):
- Phase 2, 12 weeks: 1 bottle by volume (6 mL required).
- Phase 2, 24 weeks: 2 bottles by volume (20 mL required).
- Phase 3, 12 weeks: 1 bottle by volume (6 mL required).
- Phase 3, 24 weeks: 2 bottles by volume (18 mL required).
- Alcohol swabs:
- Phase 2, 12 weeks: 24 swabs minimum; 1 box of 100 covers the calculation.
- Phase 2, 24 weeks: 60 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: 56 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.
Retatrutide 20 mg
Research-labeled vial
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Retatrutide Vial and Research Context
- Reconstitute: Add 2 mL of bacteriostatic water to produce 10 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 = 100 mcg.
- Vial size: The 20 mg label is total nominal vial content, not a weekly amount.
- Vial coverage: At the 2 mg research stage, one vial supplies 10 full weekly amounts. At the 12 mg research stage, one vial supplies 1 full weekly amount with 8 mg remaining. These are mass calculations, not vial storage or discard periods.
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: 20 mg divided by 2 mL equals 10 mg/mL.
- Unit conversion: 1 U-100 unit equals 100 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
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 20 mg vial. It is educational information and not individualized medical advice.
References
- 1New England Journal of Medicine (2023): Triple-Hormone-Receptor Agonist Retatrutide for Obesity: randomized phase 2 trial
- 2Diabetes, Obesity and Metabolism (2026): TRIUMPH Phase 3 trial design, target doses, and escalation
- 3The Lancet (2026): TRANSCEND-T2D-1 randomized phase 3 retatrutide trial
- 4Cell Metabolism (2022): Discovery and translational pharmacology of LY3437943
- 5The Lancet (2023): Retatrutide for type 2 diabetes: randomized phase 2 trial
- 6ClinicalTrials.gov: Phase 2 retatrutide obesity study NCT04881760
- 7Current Obesity Reports (2025): Triple agonism-based therapies for obesity
- 8Nature Reviews Endocrinology (2024): Multi-receptor agonists for metabolic disease
- 9Diabetes Care (2024): Incretin-based therapies and cardiovascular considerations
- 10New England Journal of Medicine (2023): Supplementary material for the phase 2 obesity trial
- 11Hepatology (2024): Triple agonism and hepatic steatosis research
- 12The Lancet (2023): Supplementary data for the phase 2 diabetes trial
- 13CDC: Subcutaneous administration guidance
- 14Johns Hopkins Arthritis Center: How to give a subcutaneous injection
- 15NCBI Bookshelf: Best practices for injections and related procedures
- 16Journal of Pharmaceutical Sciences (2018): Stability considerations during freeze-thaw cycles