The Complete Guide to Peptide Reconstitution & Dosing

1. What Is Peptide Reconstitution?

Reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide powder into a liquid solvent — typically bacteriostatic water (BAC water) — to create an injectable solution. Peptides are shipped as a dry powder because the lyophilized form is far more stable at room temperature during transit. Once reconstituted, the peptide becomes a clear liquid solution ready for subcutaneous injection.

The reconstitution process determines three critical values that govern every subsequent dose calculation:

• 1. Concentration (mg/mL) — how much peptide is dissolved per milliliter of solution
• 2. Micrograms per unit (mcg/unit) — how much peptide each tick mark on your syringe represents
• 3. Units to draw — the exact number of syringe units needed for your desired dose

Getting these calculations right is essential. Too much water dilutes the solution, potentially making accurate measurement difficult with larger syringe sizes. Too little water creates a highly concentrated solution where a single tick mark represents a large dose, increasing the risk of measurement error.

2. Bacteriostatic Water: What It Is and Why It Matters

Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits bacterial growth, which is why BAC water is the preferred solvent for peptides that will be stored and used over multiple days.

Storage: Unopened BAC water should be stored at room temperature (15-30°C). After opening, store at 2-8°C (refrigerator) and use within 28 days. Always use a fresh alcohol wipe on the rubber stopper before each use to maintain sterility.

3. The Concentration Formula

The reconstitution formula is straightforward — concentration is simply the peptide mass divided by the water volume:

For example, a 5 mg vial reconstituted with 2 mL of bacteriostatic water yields a concentration of 2.5 mg/mL, which equals 2,500 mcg/mL.

The more water you add, the more dilute the solution becomes — and the more syringe units you'll need to draw for a given dose. The less water you add, the more concentrated the solution — and fewer units needed per dose, but with less room for measurement precision.

4. Micrograms per Syringe Unit

On a standard U-100 insulin syringe (the most commonly used for peptides), 100 units = 1 mL. Therefore each "unit" equals 0.01 mL. Once you know the concentration, calculating micrograms per unit is simple:

For a 2.5 mg/mL solution: (2.5 × 1000) ÷ 100 = 25 mcg per unit. This means each tick mark on a U-100 syringe delivers 25 mcg of peptide. For a dose of 250 mcg, you would draw 10 units (250 ÷ 25 = 10 units).

5. Choosing the Right Syringe Size

Insulin syringes come in three standard sizes. The right choice depends on your dose volume:

Pro tip: For most peptide doses (100-500 mcg), the 0.3 mL (30-unit) syringe offers the finest graduation marks and best accuracy. Use our Reverse Calculator to find the optimal water volume that brings your dose into the 5-20 unit range on a 30-unit syringe.

6. Step-by-Step Reconstitution Process

1. 1

   Prepare your workspace

   Clean surface, alcohol wipes, peptide vial, BAC water vial, syringe, and sharps container.

2. 2

   Calculate your water volume

   Use the concentration formula or our calculator to determine how much BAC water to add. More water = easier to measure small doses.

3. 3

   Wipe the vial stoppers

   Use an alcohol wipe on both the peptide vial and BAC water vial rubber stoppers. Let dry for 10 seconds.

4. 4

   Draw BAC water

   Using a fresh syringe, draw the calculated amount of BAC water. For 2 mL, use a standard 3 mL syringe (not an insulin syringe).

5. 5

   Inject water slowly

   Insert the needle into the peptide vial at a slight angle, aiming the water stream down the inside wall of the vial — NOT directly onto the peptide cake. Release the water slowly.

6. 6

   Swirl gently to dissolve

   Do NOT shake the vial. Gently roll or swirl until the powder is fully dissolved. The solution should be clear. If cloudy, continue gentle swirling.

7. 7

   Label and refrigerate

   Label the vial with: peptide name, concentration, reconstitution date, and discard date (28 days). Store at 2-8°C.

7. How to Calculate Your Dose in Units

Once you know the mcg per unit from your reconstitution, calculating your dose is division:

Example: You want a 250 mcg dose of BPC-157. Your 5 mg vial was reconstituted with 2 mL of BAC water, giving 25 mcg/unit. → 250 ÷ 25 = 10 units on a U-100 syringe. Use our Reconstitution Calculator to do this instantly.

8. Worked Examples for Popular Peptides

9. Storage & Shelf Life Guidelines

10. Multi-Peptide Stacks & Blends

Many users combine two or more peptides in a stack for synergistic effects. Each peptide is reconstituted and drawn separately, then injected at the same site (or different sites depending on preference).

Use our Blend / Stack Calculator to plan multi-peptide reconstitution and track individual doses across your stack.

11. Frequently Asked Questions