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Peptide reconstitution calculator

Enter your vial amount and desired dose to instantly calculate how many units to draw on your syringe. Works for any reconstituted peptide or premixed medication.

By OptiPin Editorial·Last updated ·Contact
How to use this calculator
1
Choose type
Powder vial or premixed liquid
2
Enter medication
Amount printed on your vial
3
Set liquid volume
How much BAC water you added
4
Enter your dose
Get exact syringe units instantly

Step 1 - What type of medication?

2

Medication in Vial

Enter the amount labeled on your vial(s)

3

Desired Dose per Injection

How much medication per injection

4

Reconstitution

Solve for

Bacteriostatic water added
2.00
mL
What liquid volume should I use?

Common choice: 1–3 mL. Most vials hold a max of ~3 mL.

• Less water → smaller injections, but harder to measure precisely

• More water → easier measurement, but larger injection volume

Always use bacteriostatic water (not saline or plain water) to preserve the peptide.

Enter your values above
Fill in the medication amount and desired dose to see your results.
Educational use only. This calculator is for informational purposes and does not constitute medical advice. Always verify dosing with your healthcare provider. Measurement errors can have serious health consequences - double-check your calculations.
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How to Use This Calculator

1
Choose your medication type

Reconstitute if you have a powder vial you'll mix with bacteriostatic water. Premixed if the medication already comes in liquid form.

2
Enter medication amount

For reconstitution: enter the mg amount printed on your vial (e.g., "5 mg BPC-157"). For premixed: enter the concentration listed (e.g., "200 mg/mL testosterone cypionate").

3
Enter your desired dose

Enter the dose you plan to inject each time (in mg or mcg).

4
Set water, or set your target units (reconstitution only)

Choose Set water → get units to enter how much bacteriostatic water you'll add and see the units to draw. Or flip to Set units → get water to pick a clean number of syringe units and have the calculator tell you how much water to add. 1–2 mL is common for most peptides.

Peptide & GLP-1 Reconstitution Chart

Common reconstitution setups and the units to draw on a U-100 insulin syringe (100 units = 1 mL). These are worked examples; use the calculator above for your exact vial and dose.

Compound Vial BAC water Concentration Example dose Draw to (units)
Semaglutide5 mg1 mL5 mg/mL0.25 mg5 units
Semaglutide5 mg1 mL5 mg/mL0.5 mg10 units
Semaglutide10 mg2 mL5 mg/mL1 mg20 units
Tirzepatide10 mg1 mL10 mg/mL2.5 mg25 units
Tirzepatide20 mg1 mL20 mg/mL5 mg25 units
Tirzepatide30 mg1.5 mL20 mg/mL7.5 mg37.5 units
Retatrutide10 mg1 mL10 mg/mL2 mg20 units
Retatrutide20 mg2 mL10 mg/mL4 mg40 units
BPC-1575 mg2 mL2.5 mg/mL250 mcg10 units
TB-5005 mg2.5 mL2 mg/mL2 mg100 units

Educational reference only, not medical advice or a recommended dose. Confirm your protocol with a licensed provider. Store reconstituted vials refrigerated and follow compound-specific discard windows.

Frequently Asked Questions

What is reconstitution?
Reconstitution means dissolving a freeze-dried (lyophilized) powder peptide into liquid - usually bacteriostatic water - to create an injectable solution. Most research peptides (BPC-157, TB-500, CJC-1295, etc.) come as powder and must be reconstituted before injection.
What does "units" mean on a syringe?
Insulin syringes measure in "units" - specifically insulin units. 100 units = 1 mL. So 10 units = 0.10 mL, 25 units = 0.25 mL. When you use an insulin syringe for peptides, you draw to the unit marking that corresponds to your calculated volume.
How much bacteriostatic water should I add?
Most practitioners use 1–2 mL for standard 5 mg peptide vials. Use this calculator to find the liquid volume that gives you an easy-to-measure number of units. For example, adding 2 mL to a 5 mg BPC-157 vial gives 2.5 mg/mL concentration. A 250 mcg dose = 10 units on a 30-unit syringe - a clean, easy measurement.
What syringe should I use?
30-unit (0.3 mL) insulin syringes are most commonly used for peptides. They allow precise measurement in small increments. 50-unit and 100-unit syringes are options if your dose requires a larger volume. Always use a fresh, sterile needle for each injection.
Can I use this for semaglutide / GLP-1 medications?
Yes - select Premixed mode and enter your concentration (e.g., 2.5 mg/mL or 5 mg/mL for compounded semaglutide, 2 mg/0.5 mL = 4 mg/mL for tirzepatide). Then enter your dose in mg. The calculator will give you the units to draw.
How do you reconstitute tirzepatide?
Add bacteriostatic water to the powder vial, then draw your dose with a U-100 insulin syringe. For a 10 mg tirzepatide vial, adding 1 mL of bacteriostatic water gives a 10 mg/mL solution, so a 2.5 mg dose is 0.25 mL, or 25 units. For a 20 mg vial with 1 mL of water (20 mg/mL), a 5 mg dose is 25 units. Inject the water slowly down the vial wall, swirl gently rather than shaking, and store the reconstituted vial refrigerated.
How do you reconstitute semaglutide?
Add bacteriostatic water to the powder vial and draw your dose on a U-100 insulin syringe. A 5 mg semaglutide vial with 1 mL of bacteriostatic water gives 5 mg/mL, so a 0.25 mg starting dose is 5 units and a 0.5 mg dose is 10 units. Add the water slowly, swirl gently instead of shaking, and keep the reconstituted vial refrigerated.

Sources & further reading

This calculator does the reconstitution arithmetic only. Concentrations of compounded vials vary by pharmacy and are not standardized; always confirm your vial's stated strength and your dose with a pharmacist or prescriber before drawing. U-100 insulin syringe: 100 units = 1 mL.