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.
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)
Draw syringe to
33 units
(0.33 mL)
Concentration:
6,000 mcg/mL
Doses per vial:
6
Your reconstitution is set — now track your GLP-1.
Regimen logs every dose of your GLP-1 — 2mg at a time, 6 doses per vial. It reminds you when to inject, tracks your reconstitution dates, and logs weight and side effects alongside your titration.
- Injection reminders for each compound
- Track reconstitution dates and vial expiry
- Track weight, side effects, and titration over time
Free for one compound. No trial, no paywall.
For educational and research purposes only. This calculator provides estimates based on standard formulas.
Always verify calculations with your healthcare provider before use. We assume no liability for dosing errors, adverse events, or outcomes resulting from use of this tool.
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
5mg Vial + 1mL BAC Water (5.0 mg/mL)
| Target Dose | Units to Draw | Doses Per Vial |
|---|---|---|
| 2 mg | 40 units | 2 doses |
| 4 mg | 80 units | 1 dose |
12mg Vial + 2mL BAC Water (6.0 mg/mL)
| Target Dose | Units to Draw | Doses Per Vial |
|---|---|---|
| 2 mg | 33 units | 6 doses |
| 4 mg | 67 units | 3 doses |
| 6 mg | 100 units | 2 doses |
30mg Vial + 3mL BAC Water (10.0 mg/mL)
| Target Dose | Units to Draw | Doses Per Vial |
|---|---|---|
| 2 mg | 20 units | 15 doses |
| 4 mg | 40 units | 7 doses |
| 8 mg | 80 units | 3 doses |
| 12 mg | 120 units | 2 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
- Swab the tops of both the retatrutide vial and the BAC water vial with alcohol. Let them dry, about 15 to 30 seconds.
- Draw your chosen volume of BAC water (typically 1 to 3mL, up to 5mL for the largest vials) into an insulin syringe.
- 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.
- Gently swirl or roll the vial between your palms. Retatrutide can take up to 8 minutes to fully dissolve. Do not shake.
- Check the solution. It should be completely clear with no particles or cloudiness before you draw your first dose.
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.
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.
How to use this calculator
Enter vial size
5, 10, 12, 15, 20, 24, or 30mg are common compounded retatrutide vial sizes
Enter BAC water volume
1 to 3mL is typical; 5mL is sometimes used for the largest vials to keep injection volume manageable
Enter target dose
Phase 2 titration tiers were 2, 4, 8, and 12mg per week
Pick your syringe
U-100 insulin syringe in 0.3, 0.5, or 1.0mL — the calculator visualizes the exact mark to draw to
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