The Complete Peptide Reconstitution Calculator Guide

If you've ever stared at a vial of lyophilized peptide and wondered how a number on a syringe maps back to milligrams, you're in the right place. This guide walks through every step, with worked examples for the most common GLP-1s and research peptides.

What is reconstitution?

Reconstitution is the process of mixing a freeze-dried peptide with bacteriostatic water (BAC water) to produce an injectable solution at a known concentration. The peptide arrives dry; you add water; you draw a known volume; that volume contains a known dose. Simple in concept — easy to mis-math in practice.

The only equation you need

Concentration (mg/mL) = mg per vial ÷ mL of BAC water

That's it. Everything else flows from this.

Once you know your concentration, picking a dose is just division:

Dose volume (mL) = target dose (mg) ÷ concentration (mg/mL)

And to map volume to syringe units:

• U-100 syringe: 1 mL = 100 units → multiply mL by 100
• U-40 syringe: 1 mL = 40 units → multiply mL by 40

Worked example: semaglutide 5 mg vial, 2 mL BAC water

1. Concentration = 5 mg ÷ 2 mL = 2.5 mg/mL
2. Target dose 0.25 mg:
   • Volume = 0.25 ÷ 2.5 = 0.10 mL
   • On a U-100 syringe = 0.10 × 100 = 10 units
3. Target dose 0.50 mg:
   • Volume = 0.50 ÷ 2.5 = 0.20 mL
   • On a U-100 syringe = 20 units

Worked example: tirzepatide 10 mg vial, 1 mL BAC water

1. Concentration = 10 mg ÷ 1 mL = 10 mg/mL
2. Target dose 2.5 mg → 25 units U-100
3. Target dose 5 mg → 50 units U-100

Worked example: BPC-157 5 mg vial, 5 mL BAC water

1. Concentration = 1 mg/mL
2. Target dose 250 mcg (0.25 mg) → 25 units U-100

Picking BAC water volume

Aim for a concentration where your typical dose lands between 10 and 50 units on a U-100 syringe.

U-100 vs U-40 syringes

Both are calibrated to milliliters underneath — the difference is the scale on the barrel. The TrackPep calculator takes the syringe type as an explicit input so it computes the right unit reading every time.

FAQ

Can I use regular sterile water?

Sterile water has no preservatives. Fine for single-use; multi-use vials require bacteriostatic water.

Does BAC water volume affect dose math?

No. The peptide mass doesn't change when you add water — only the concentration.

Skip the math entirely

The free TrackPep reconstitution calculator does all of this in your browser, no signup.

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Informational only. Always consult a licensed healthcare professional.