Download

Retatrutide Reconstitution Calculator

Enter your vial size, BAC water volume, and target weekly dose. The calculator returns exact insulin units, mg/mL concentration, doses per vial, and a draw-to-here syringe diagram.

Last updated August 2026 · Reviewed by the Regimen Team

Peptide reconstitution

Peptide Reconstitution Calculator

Calculate your exact dose

Enter your vial details to calculate how many units to draw for your dose.

Common doses: Semaglutide (0.25-2.4mg), Tirzepatide (2.5-15mg)

This calculator is for informational purposes only, so always double-check your result with a healthcare provider. We assume no liability for dosing errors.

How to use it

How to use this calculator

  1. 01

    Enter vial size

    5, 10, 12, 15, 20, 24, or 30mg are common compounded retatrutide vial sizes

  2. 02

    Enter BAC water volume

    1 to 3mL is typical; 5mL is sometimes used for the largest vials to keep injection volume manageable

  3. 03

    Enter target dose

    Phase 2 titration tiers were 2, 4, 8, and 12mg per week

  4. 04

    Pick your syringe

    U-100 insulin syringe in 0.3, 0.5, or 1.0mL - the calculator visualizes the exact mark to draw to

Dose Calculation: The Math Explained

The formula is the same for any reconstituted peptide:

Concentration = Total peptide (mg) ÷ BAC water added (mL)
Units = (Target dose in mg ÷ Concentration in mg/mL) × 100

Worked example. A 12mg vial reconstituted with 2mL of BAC water has a concentration of 12 ÷ 2 = 6 mg/mL. For a 4mg weekly dose: (4 ÷ 6) × 100 = 66.7 units. Round to 67 units. That 12mg vial at 4mg per week gives you 3 weekly doses, roughly 3 weeks per vial.

Common Vial Sizes and Dose Charts

Among Regimen users tracking retatrutide, the most common vial is 10mg (39%), followed by 20mg (23%) and 30mg (16%). Most reconstitute with 2mL of bacteriostatic water (41%), then 1mL (28%) and 3mL (26%). The most commonly logged weekly dose is 2mg.

5mg Vial + 1mL BAC Water (5.0 mg/mL)

Target DoseUnits to DrawDoses Per Vial
2 mg40 units2 doses
4 mg80 units1 dose

10mg Vial + 1mL BAC Water (10.0 mg/mL)

Target DoseUnits to DrawDoses Per Vial
2 mg20 units5 doses
4 mg40 units2 doses
8 mg80 units1 dose

12mg Vial + 2mL BAC Water (6.0 mg/mL)

Target DoseUnits to DrawDoses Per Vial
2 mg33 units6 doses
4 mg67 units3 doses
6 mg100 units2 doses

20mg Vial + 2mL BAC Water (10.0 mg/mL)

Target DoseUnits to DrawDoses Per Vial
2 mg20 units10 doses
4 mg40 units5 doses
8 mg80 units2 doses
12 mg120 units1 dose

30mg Vial + 3mL BAC Water (10.0 mg/mL)

Target DoseUnits to DrawDoses Per Vial
2 mg20 units15 doses
4 mg40 units7 doses
8 mg80 units3 doses
12 mg120 units2 doses

Titration Schedule

The Phase 2 retatrutide trial used a slow titration: 2mg per week for 4 weeks, then 4mg for 4 weeks, then 8mg for 4 weeks, then 12mg as maintenance. Not everyone reaches 12mg. Many people stabilize at 4 or 8mg per week once appetite and weight loss are where they want them. Hold any tier longer if GI side effects do not settle within a week of dose increase.

Storage After Reconstitution

Reconstituted retatrutide is generally considered stable for 28 to 30 days when refrigerated between 36 and 46°F (2 to 8°C). Keep the vial upright, away from light, and never freeze it. Discard if the solution becomes cloudy, develops particles, or changes color. Match vial size to your weekly dose so you finish the vial inside that window - large vials at small doses waste compound.

Mixing Steps

  1. Swab the tops of both the retatrutide vial and the BAC water vial with alcohol. Let them dry, about 15 to 30 seconds.
  2. Draw your chosen volume of BAC water (typically 1 to 3mL, up to 5mL for the largest vials) into an insulin syringe.
  3. Insert the needle into the retatrutide vial at an angle and let the water run slowly down the inside glass wall. Do not aim directly at the powder.
  4. Gently swirl or roll the vial between your palms. Retatrutide can take up to 8 minutes to fully dissolve. Do not shake.
  5. Check the solution. It should be completely clear with no particles or cloudiness before you draw your first dose.

See also: full retatrutide reconstitution guide, retatrutide dosing guide, titration schedule, injection sites, side effects, and switching from tirzepatide.

Educational reference only. Not medical advice. Retatrutide is investigational and not FDA approved. Work with a licensed clinician on dosing and monitoring.

Get the app

Track your retatrutide protocol, not just the math

Regimen logs each retatrutide injection alongside your weight, side effects, and titration schedule, with injection reminders and reconstitution-date tracking.

  • Built-in dose calculators
  • Smart injection reminders
  • Track weight and side effects
  • Private, secure health data
Download on the App Store Get it on Google Play

Free to download. Free for your first compound.

Regimen app Today view with doses and estimated levels

Questions

Frequently Asked Questions

How much BAC water do I mix with a 12mg retatrutide vial?
2mL of bacteriostatic water is the standard for a 12mg vial. That gives a concentration of 6 mg/mL. At that concentration, 2mg = 33 units, 4mg = 67 units, 6mg = 100 units (the full 1mL barrel). If you need to dose above 6mg per injection from a 12mg vial, use 3mL of BAC water instead.

How much BAC water for a 5mg retatrutide vial?
1mL of BAC water gives a 5 mg/mL concentration: 2mg = 40 units, 4mg = 80 units, 5mg = 100 units. The 5mg vial is most useful during the early titration tiers (2 to 4mg per week).

How much BAC water for a 10mg retatrutide vial?
2mL is standard, giving 5 mg/mL: 2mg = 40 units, 4mg = 80 units. With 1mL of water you get 10 mg/mL, where 2mg = 20 units and 4mg = 40 units. Use the higher concentration if you want doses to sit lower on the syringe and finish the vial faster.

How much BAC water for a 15mg retatrutide vial?
2mL gives 7.5 mg/mL: 2mg = 27 units, 4mg = 53 units, 8mg = 107 units (over the 1mL barrel - split or use a larger BAC volume). 3mL gives 5 mg/mL: 2mg = 40 units, 4mg = 80 units, 8mg = 160 units (split into two injections or use a larger syringe).

How much BAC water for a 30mg retatrutide vial?
2mL gives 15 mg/mL: 2mg = 13 units, 4mg = 27 units, 8mg = 53 units, 12mg = 80 units. 3mL gives 10 mg/mL: 2mg = 20 units, 4mg = 40 units, 8mg = 80 units, 12mg = 120 units. Confirm you can finish the vial within 28 to 30 days at your current weekly dose before reconstituting a 30mg vial.

What syringe should I use for retatrutide?
A U-100 insulin syringe is standard. Pick the barrel size by your dose volume: 0.3mL (30 units) for the smallest microdoses, 0.5mL (50 units) for typical titration doses, 1.0mL (100 units) for higher doses. All three are calibrated the same way (100 units = 1mL); the smaller barrels just make small dose marks easier to read.

How many units is 2mg of retatrutide?
It depends on your concentration. At 5 mg/mL it is 40 units. At 6 mg/mL it is 33 units. At 7.5 mg/mL it is 27 units. At 10 mg/mL it is 20 units. At 15 mg/mL it is 13 units. The same dose lands at a different mark depending on how much BAC water you used.

How many units is 4mg of retatrutide?
At 5 mg/mL it is 80 units. At 6 mg/mL it is 67 units. At 7.5 mg/mL it is 53 units. At 10 mg/mL it is 40 units. At 15 mg/mL it is 27 units.

How many units is 8mg of retatrutide?
At 10 mg/mL it is 80 units. At 12 mg/mL it is 67 units. At 15 mg/mL it is 53 units. If your concentration produces a unit count above 100 in a single 1mL syringe, mix the vial with more BAC water or split the injection.

What is the starting dose for retatrutide?
The Phase 2 trial started all participants at 2mg per week for the first 4 weeks. This is the consensus starting dose across providers prescribing compounded retatrutide. The 2mg phase is for tolerance - do not expect significant appetite suppression yet. Skipping it sharply increases nausea risk.

Is it safe to use a 30mg vial if I am only dosing 2mg per week?
Mathematically a 30mg vial at 2mg per week lasts 15 weeks, but reconstituted retatrutide is only stable for about 28 to 30 days refrigerated. You would waste most of the vial. Use a 5mg or 10mg vial during early titration and move to larger vials once you reach a maintenance dose that will finish the vial inside that window.

Related tools

Tirzepatide Reconstitution Calculator Enter your vial size and how much BAC water you added. GLP-1 Dose Calculator The semaglutide reconstitution calculator and tirzepatide reconstitution calculator in one tool. GLP-1 Titration Planner Plan your Semaglutide or Tirzepatide dose escalation with personalized dates for each step. Full Retatrutide Reconstitution Guide Retatrutide Dosing Guide Titration Schedule Injection Sites Side Effects Switching from Tirzepatide GLP-1 Tracker App The GLP-1 tracker that connects your medication to real weight loss results. All Tools Six precision calculators handle the math behind any peptide, TRT, GLP-1, or HRT protocol: peptide reconsti...