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Retatrutide Dosing Calculator

28.7% body weight loss in Phase 3 TRIUMPH-4 at 68 weeks (Dec 2025) -- see dosing, side effects, FDA approval timeline.

Pre-filled with the most-reported community reconstitution protocol for Retatrutide. See how 1 mL and 2 mL of bacteriostatic water change concentration and syringe-draw volume, then adjust the calculator below for your own vial.

Quick answer · Community-reported standard

A 15 mg vial of Retatrutide reconstituted with 2 mL of bacteriostatic water yields a concentration of 7.50 mg/mL. At that concentration, a 1 mg dose of Retatrutide equals 13.3 units on a U-100 insulin syringe (0.133 mL). Retatrutide is typically administered once weekly via subcutaneous.

Retatrutide reconstitution: 1 mL vs 2 mL bac water

Bacteriostatic water volume is flexible. Less water means higher concentration and smaller injection volumes; more water means lower concentration and easier dose precision. Both options below are valid for a 15 mg vial.

BAC water addedConcentrationVolume per 1 mg doseDraw on U-100 syringe (units)
1 mL15.00 mg/mL0.067 mL6.7 units
2 mL7.50 mg/mL0.133 mL13.3 units
Based on a 15 mg vial of Retatrutide reconstituted with bacteriostatic water. Insulin-syringe units assume a standard U-100 syringe (100 units = 1 mL).

Calculate your Retatrutide dose

Alternative Retatrutide protocols

Beyond the default above, Retatrutide is also reported in the following protocols. Use these as starting points and recalculate with the tool above.

Conservative Start Protocol

Community
Dose
0.5-4 mg
Frequency
Once weekly
Duration
12-24 weeks
Route
Subcutaneous

Some community members start at sub-clinical doses (0.5 mg) and escalate more slowly than clinical protocols to assess individual tolerance

Moderate Dose Maintenance

Community
Dose
4-8 mg
Frequency
Once weekly
Duration
Ongoing
Route
Subcutaneous

Users report significant weight loss and appetite suppression at 4-8 mg without needing to reach 12 mg; lower doses may reduce GI and other side effects

Phase 2 Dose Escalation (Obesity Trial - NCT04881760)

Clinical
Dose
Starting dose 0.5 mg weekly, escalated over 12-24 weeks to target doses (1 mg, 4 mg, 8 mg, or 12 mg)
Frequency
Once weekly subcutaneous injection
Duration
48-week treatment period

Investigational protocol only; not for clinical use outside trials

Phase 2 Type 2 Diabetes Trial

Clinical
Dose
Starting dose 0.5 mg weekly, escalated to target doses up to 12 mg
Frequency
Once weekly subcutaneous injection
Duration
36-week treatment period

Investigational protocol in patients with type 2 diabetes; background metformin permitted

Retatrutide reconstitution & storage

Investigational formulation; details not publicly available for clinical use

Investigational product; storage per clinical trial protocol

Retatrutide dosing FAQ

How much bacteriostatic water should I add to a 15 mg vial of Retatrutide?

The community standard is 2 mL of bacteriostatic water for a 15 mg Retatrutide vial. That gives a concentration of 7.50 mg/mL, so a 1 mg dose is 13.3 units on a U-100 insulin syringe. Adding 1 mL instead doubles the concentration to 15.00 mg/mL and halves the draw to 6.7 units. Less water = smaller injection volume but harder to measure precisely.

How many syringe units is a 1 mg dose of Retatrutide?

On a standard U-100 insulin syringe, a 1 mg dose of Retatrutide is 13.3 units when the 15 mg vial is reconstituted with 2 mL of bacteriostatic water (7.50 mg/mL). If you use 1 mL of bac water instead, draw 6.7 units (15.00 mg/mL).

What is the standard Retatrutide dose?

Community-reported protocols for Retatrutide typically use 1 mg–12 mg once weekly via Subcutaneous. 1 mg is a common starting dose. Based on Phase 2 trial schedule: 1 mg x4 weeks, 2 mg x4 weeks, 4 mg x4 weeks, escalating up to 8 or 12 mg; community users attempt to replicate clinical dosing

How long does a vial of Retatrutide last at 1 mg once weekly?

A 15 mg vial of Retatrutide contains roughly 15 doses at 1 mg per injection. At once weekly dosing, that is approximately 105 days (about 15 weeks) of supply per vial. Reconstituted Retatrutide should generally be used within 28 days when refrigerated.

Where do you inject Retatrutide?

Retatrutide is typically injected subcutaneous. Common sites reported in the literature and by users include: Subcutaneous (abdomen), Subcutaneous (thigh). Rotate sites with each injection to reduce localized irritation.

Can I use sterile water instead of bacteriostatic water for Retatrutide?

Bacteriostatic water (containing 0.9% benzyl alcohol as a preservative) is strongly preferred for multi-dose vials like Retatrutide because it inhibits microbial growth and lets a single vial be used over multiple weeks. Sterile water has no preservative and should generally be reserved for single-use preparations only.

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Medical Disclaimer

This website is for educational and informational purposes only. The information provided is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before using any peptide or supplement.