How to Reconstitute Peptides
Lyophilized (freeze-dried) peptides have to be mixed with bacteriostatic water before they can be measured and administered. This guide walks through the supplies, the sterile technique, how much water to add, how to store the vial, and how to read your dose in insulin-syringe units.
Not medical advice. This is general educational information about the mechanics of reconstitution. It does not recommend any peptide, dose, or protocol, and it does not replace the instructions from your licensed provider or pharmacy, which always take precedence.
What you'll need
- The lyophilized peptide vial
- Bacteriostatic water (sterile water with 0.9% benzyl alcohol)
- A sterile mixing syringe (a 1–3 mL syringe with a drawing needle)
- The insulin syringes you'll dose with (U-100 is standard)
- Alcohol wipes and a clean, flat surface
Step by step
Wash your hands, lay out your supplies, and wipe the stopper of both the peptide vial and the water vial with a fresh alcohol wipe.
The water sets the concentration, not the dose. Decide the volume first — the calculator helps you land clean syringe marks.
Pull your chosen volume of bacteriostatic water into the sterile mixing syringe.
Insert the needle through the peptide vial's stopper and let the water run gently down the inside glass wall — never jet it onto the powder.
Gently swirl or roll until the solution is completely clear. Shaking foams and can degrade the peptide.
Write the date and concentration on the vial, refrigerate it, and track doses and remaining volume in the app.
How much water should I add?
This is the question everyone asks, and the answer surprises people: the amount of water doesn't change your dose at all. The peptide amount in the vial is fixed. Water only changes the concentration — and therefore how many units you draw to reach the same dose.
- More water → lower concentration → a larger, easier-to-read draw for small doses.
- Less water → higher concentration → a smaller draw, useful when a dose would otherwise overfill the syringe.
The goal is to pick a water volume that puts your provider-directed dose on a clean, easy-to-read mark. Our reconstitution calculator shows the exact draw live on an animated syringe, and there are presets for common compounds: semaglutide, tirzepatide, retatrutide, BPC-157, and TB-500.
Reading the dose in syringe units
A standard U-100 insulin syringe holds 100 units per millilitre, so once you know the volume to draw in mL, the unit reading is simply that volume × 100. Worked example:
| Vial amount | 5 mg = 5,000 mcg |
| Water added | 2 mL |
| Concentration | 5,000 ÷ 2 = 2,500 mcg/mL |
| Dose | 250 mcg |
| Volume to draw | 250 ÷ 2,500 = 0.10 mL |
| On the syringe | 0.10 × 100 = 10 units |
Storage & handling
Most reconstituted peptides are kept in the refrigerator, away from light, and used within the window your provider or pharmacy specifies. Label the vial with the reconstitution date and concentration so you always know its age and how many doses remain. Track the reconstitution date, inventory, and expiration in the PeptideWiz app so it reminds you before a vial runs out or expires.
Frequently asked questions
What is bacteriostatic water and why is it used?
It's sterile water with 0.9% benzyl alcohol, a preservative that inhibits bacterial growth. That's what lets a reconstituted multi-dose vial be used over several refrigerated days, which is why it's preferred over plain sterile water. See bacteriostatic water.
How much bacteriostatic water should I add?
There's no single right amount — water sets the concentration, not the dose. Pick a volume that lands your dose on easy-to-read syringe marks, and check it with the calculator.
Why swirl instead of shake?
Peptides are fragile. Shaking foams the solution and can degrade the molecule; a gentle swirl or roll dissolves the powder without damage.
How should I store a reconstituted peptide?
Refrigerated, protected from light, and used within the window your provider or pharmacy gives you. Label the vial with the date and concentration to track its age and remaining doses.
Track reconstitution, inventory & reminders in PeptideWiz →