Last updated: May 2026

Retatrutide Dosage Calculator

Quick answer: A 4 mg dose from a 10 mg/mL vial is 0.40 mL = 40 units on a U-100 syringe. Formula: Volume (mL) = Dose (mg) ÷ Concentration (mg/mL), then units = mL × 100.

About this calculator

The retatrutide draw volume calculator converts a prescribed dose into the volume to draw from a compounded vial using Volume (mL) = Dose (mg) ÷ Concentration (mg/mL). Built for people using compounded retatrutide vials with an insulin syringe. Supports common concentrations from 1–20 mg/mL. Free, instant, no login.

Retatrutide is a triple GIP/GLP-1/glucagon receptor agonist under development by Eli Lilly. It is not yet FDA-approved. Compounded versions are investigational. Always use under medical supervision.

How to use this calculator

You need two pieces of information: your vial concentration (printed on the pharmacy label in mg/mL) and your prescribed dose in mg. Select your concentration using the barrel picker, and your dose using the dose barrel. Draw volume and U-100 units update instantly after pressing Calculate.

Always verify the drawn volume against your syringe markings before injecting. This calculator assumes a U-100 insulin syringe (1 unit = 0.01 mL).

Worked example

Example — 4 mg dose from a 10 mg/mL vial

Vial concentration: 10 mg/mL

Prescribed dose: 4 mg

Draw = 4 ÷ 10 = 0.40 mL = 40 units (U-100 syringe)

Example — 2 mg dose from a 5 mg/mL vial

Vial concentration: 5 mg/mL

Prescribed dose: 2 mg

Draw = 2 ÷ 5 = 0.40 mL = 40 units (U-100 syringe)

Common dose reference table

Dose2.5 mg/mL vial5 mg/mL vial10 mg/mL vial
1 mg0.40 mL (40 U)0.20 mL (20 U)0.10 mL (10 U)
2 mg0.80 mL (80 U)0.40 mL (40 U)0.20 mL (20 U)
4 mg1.60 mL (160 U)0.80 mL (80 U)0.40 mL (40 U)
6 mg2.40 mL (240 U)1.20 mL (120 U)0.60 mL (60 U)
8 mg3.20 mL (320 U)1.60 mL (160 U)0.80 mL (80 U)
12 mg4.80 mL (480 U)2.40 mL (240 U)1.20 mL (120 U)

Frequently asked questions

How do I calculate retatrutide dosage from a compounded vial?
Divide your prescribed dose in mg by your vial concentration in mg/mL. For example, a 4 mg dose from a 10 mg/mL vial equals 4 ÷ 10 = 0.40 mL, which is 40 units on a U-100 insulin syringe. The calculator performs this division automatically. Always confirm the concentration on your specific pharmacy label.
What is retatrutide and how does it differ from tirzepatide and semaglutide?
Retatrutide is a triple GIP/GLP-1/glucagon receptor agonist. Tirzepatide is a dual GIP/GLP-1 agonist; semaglutide is a GLP-1 agonist only. The added glucagon receptor activity in retatrutide may increase energy expenditure beyond GLP-1 alone. Phase 2 trials showed up to 24% weight loss at 48 weeks. It is not yet FDA-approved — compounded versions are investigational. Use under medical supervision only.
What dose of retatrutide should I start at?
Clinical trials started at 1 mg per week, stepping up over several months to maintenance doses of 4–12 mg per week. The maximum studied dose was 12 mg per week. Always follow your prescriber’s written protocol and never self-adjust dosing.

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Related guides

Retatrutide calculator guide → What are GLP-1 medications? → Why GLP-1 doses increase over time → GLP-1 titration planner → How to read an insulin syringe → Retatrutide vs tirzepatide dosing →

How this is calculated

This calculator divides your prescribed dose by the vial concentration to find the injection volume, then converts that volume to insulin-syringe units (volume in mL × 100 for a U-100 syringe). It is arithmetic only — nothing you enter is stored or sent anywhere, and the result is not medical advice. Always confirm your dose with your prescriber.

Built by the InjectBuddy team — developer, not a medical professional. InjectBuddy performs standard volume and ratio calculations based on your inputs. These calculators do not constitute medical advice — always verify dosing with your prescribing doctor or pharmacist. Retatrutide is investigational and not FDA-approved.

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References

Retatrutide is investigational and not FDA-approved. Any dosing shown comes from a phase-2 trial, not an approved label.

  1. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial — N Engl J Med, 2023
  2. FDA Concerns With Unapproved GLP-1 Drugs Used for Weight Loss — U.S. FDA
  3. FDA Green List: Protecting Americans From Illegal Imported GLP-1 Drug Ingredients — U.S. FDA

Citations are provided for transparency and education. They do not imply the cited authors or bodies endorse this tool. Always confirm dosing with your prescriber.