Reconstitution Guide · 2026

Peptide Reconstitution:
The Complete Guide

The math is 30 seconds. The equipment costs 2. Getting it wrong means every dose is off by a factor you can't measure. Here is exactly how to do it correctly — for any peptide, any vial size.

The Concept

What Reconstitution Is and Why It Matters

Research peptides are shipped as lyophilized (freeze-dried) powder because they are stable in dry form for months to years. Injectable solutions are not stable — they degrade faster in liquid form. Reconstitution converts the stable powder into a stable injectable solution by adding bacteriostatic water (BAC water), which contains benzyl alcohol as a preservative.

The volume of BAC water you add determines the concentration of the resulting solution. Concentration determines how many units to draw on your syringe for each dose. If you add the wrong BAC water volume, every dose you inject is at a different concentration than you calculated — and there's no visible indicator that anything is wrong.

The Reconstitution Formula

Concentration (mcg/mL) = Vial size (mcg) ÷ BAC water (mL)

Draw units = (Dose mcg ÷ Concentration mcg/mL) × 100

Example: 5mg vial + 2mL BAC water = 2,500 mcg/mL. For 250mcg dose: (250 ÷ 2,500) × 100 = 10 units on a U-100 syringe.

Equipment Required

What You Need Before You Start

Protocol peptide reconstitution calculator showing precise calculation with easy draw mode output

Protocol's reconstitution calculator — enter vial size, BAC water, and dose to get exact draw units

Every reconstitution requires: the peptide vial, bacteriostatic water (NOT sterile water for multi-dose use), a drawing syringe (1mL or 3mL for adding BAC water), your dosing syringe (U-100 insulin syringe, 28–31 gauge), and alcohol swabs. That is the complete list.

The critical detail: bacteriostatic water, not sterile water. Sterile water has no preservative. If you use sterile water, the reconstituted peptide should be used within 24 hours and discarded — the benzyl alcohol in BAC water is what prevents bacterial contamination across 20–40 draws over 30 days. BAC water is available from research chemical suppliers and some pharmacies.

Most people use 1mL insulin syringes (U-100) for both adding BAC water and dosing. This works if you only need to add 1mL. For 2mL+ additions, use a separate 3mL drawing syringe for the BAC water step, then your insulin syringe for dosing. Do not try to add 2mL through a 1mL syringe in two passes — it increases contamination risk.

Step by Step

Reconstitution Procedure

01
Gather supplies and set up a clean surface

Peptide vial, BAC water, drawing syringe, alcohol swabs, labeling materials. Work on a clean flat surface away from high-traffic areas.

02
Swab both stoppers

Wipe the stopper of the peptide vial and the BAC water vial with a fresh alcohol swab. Allow 10–15 seconds to dry. Do not touch the center of the stopper after swabbing.

03
Draw the BAC water

Insert the drawing syringe needle at an angle into the BAC water vial stopper. Slowly withdraw the calculated volume of BAC water. For 2mL standard: draw two full 1mL syringes or use one 3mL syringe.

04
Add BAC water slowly, down the glass wall

Insert the needle into the peptide vial stopper. Tilt the vial so the needle tip touches the inner glass wall. Release the BAC water slowly so it runs down the side — not directly onto the powder. This prevents mechanical disruption of the peptide.

05
Swirl gently — do not shake

Gently rotate the vial in a circular motion until the powder dissolves. The solution should be clear and colorless. Most peptides dissolve in 30–90 seconds. Do not shake — shaking can cause foaming and mechanical peptide degradation.

06
Label and refrigerate

Write the reconstitution date, BAC water volume, and calculated concentration on the vial. Store at 2–8°C (standard refrigerator). Reconstituted peptide in BAC water is stable for 28–30 days refrigerated.

Reference Data

Reconstitution Reference — Common Vial Sizes

These are the most common vial sizes and BAC water volumes, with the resulting concentrations and draw units for standard dose ranges.

Vial SizeBAC WaterConcentration250mcg Dose500mcg Dose
5mg2mL2,500 mcg/mL10 units20 units
5mg4mL1,250 mcg/mL20 units40 units
10mg2mL5,000 mcg/mL5 units10 units
10mg4mL2,500 mcg/mL10 units20 units
2mg1mL2,000 mcg/mL12.5 units25 units
2mg2mL1,000 mcg/mL25 units50 units

All draw unit calculations assume a U-100 insulin syringe (100 units = 1mL). Use the free calculator at reconstitution.health for any vial size or dose.

Common Questions

FAQ

What is bacteriostatic water and where do I get it?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol. The benzyl alcohol acts as a preservative, preventing bacterial growth across multiple needle insertions. This makes it safe for multi-dose peptide vials over 28–30 days. It's available from research chemical suppliers, some compounding pharmacies, and specialty medical supply sources. Do not substitute plain sterile water for multi-dose vials — it lacks the preservative and the reconstituted solution should be used within 24 hours.
How do I know if I used the wrong BAC water volume?
You usually can't tell visually — a correctly and incorrectly reconstituted vial look identical. The only way to catch an error is to recalculate before drawing. If your syringe draw looks unexpectedly small (under 5 units) or unexpectedly large (over 40 units) for a standard peptide dose, recheck your BAC water volume and concentration math. Doses below 5 units are difficult to measure accurately on a U-100 syringe — adding more BAC water to raise the draw units to 10–20 is the standard fix.
What is the Custom Draw reconstitution calculator?
Custom Draw is Protocol's reverse reconstitution calculator, available at reconstitution.health. Standard mode: enter vial size, BAC water, and dose — get draw units. Custom Draw mode: enter the draw units you want per dose — get the BAC water volume needed to produce that draw at your dose. This is particularly useful when you prefer a specific syringe graduation (e.g., exactly 20 units) and want to build the reconstitution around it rather than adjusting to whatever draw a standard calculation produces.
How long does reconstituted peptide last?
Reconstituted peptide in bacteriostatic water, stored refrigerated at 2–8°C, is stable for approximately 28–30 days. Lyophilized (unreconstituted) peptide stored in the freezer at -20°C or in a cool dark environment is stable for 12–24 months. Do not freeze a reconstituted vial — freezing can cause peptide aggregation and reduce potency. Label every reconstituted vial with the date.
Why must I add BAC water down the side of the vial?
Adding water directly onto lyophilized powder can cause mechanical disruption — the pressure and turbulence of the water stream can physically break peptide bonds or cause denaturation in sensitive peptides. Running the water down the glass wall creates a gentler, more even hydration process. The peptide dissolves as the water level rises around it rather than being blasted with a stream. This is a precautionary step, not an absolute requirement for all peptides, but it's the correct technique for any freeze-dried injectable.

Free Reconstitution Calculator

Custom Draw mode · Any vial size · No download required

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