Peptide Reconstitution Calculator: BAC Water Math Made Simple

Peptide reconstitution math is not complicated — but it trips up more people than any other aspect of peptide research. The mistakes are expensive: add too much water and your doses become impractically large. Add too little and you can't measure accurately with standard syringes. Get the numbers wrong entirely and you're taking the wrong dose for your entire protocol.

This guide provides the math, the reference tables, and the step-by-step process to get it right the first time.

The Universal Reconstitution Formula

Every peptide reconstitution follows the same three steps:

Step 1: Know your vial size (e.g., 5mg, 10mg, 15mg).

Step 2: Choose your BAC water volume. This determines the concentration.

Step 3: Calculate the volume to draw for your desired dose.

The formula: Peptide amount (mg) ÷ BAC water added (mL) = Concentration (mg/mL)

Then: Desired dose (mcg) ÷ Concentration (mcg/mL) = Volume to inject (mL)

Note: 1 mg = 1,000 mcg. Keep your units consistent.

Quick Reference Table: Common Vial Sizes

Understanding Insulin Syringe Markings

Standard U-100 insulin syringes measure in "units" where 100 units = 1 mL. This means:

10 units = 0.10 mL. 5 units = 0.05 mL. 1 unit = 0.01 mL.

The most common syringe sizes for peptide research:

0.3 mL (30 unit) syringes: Best for small doses. Each small tick mark = 0.5 units (0.005 mL). Excellent accuracy at low volumes. Ideal for concentrated reconstitutions.

0.5 mL (50 unit) syringes: Good middle ground. Each small tick = 1 unit (0.01 mL). Works well for most standard protocols.

1.0 mL (100 unit) syringes: Each small tick = 2 units (0.02 mL). Best for larger-volume injections or dilute reconstitutions. Less precise at small volumes — avoid for doses under 10 units.

Step-by-Step Reconstitution Process

Supplies Needed

• Peptide vial (lyophilized)
• Bacteriostatic water (BAC water — 0.9% benzyl alcohol)
• Alcohol swabs
• Insulin syringes (separate for reconstitution and dosing)

Process

1. Clean: Swab the tops of both the peptide vial and BAC water vial with alcohol. Let air dry (5–10 seconds).

2. Draw BAC water: Using a syringe, draw your chosen volume of BAC water. For a 5mg vial, 2 mL is a good standard choice — it creates an easy concentration to work with.

3. Add slowly: Insert the needle through the peptide vial's rubber stopper. Direct the water stream onto the inside wall of the vial — not directly onto the lyophilized powder. Depress the plunger slowly.

4. Dissolve gently: Do NOT shake. Gently swirl the vial or roll it between your palms. Most peptides dissolve in 1–3 minutes. If powder remains after 5 minutes of gentle swirling, let the vial sit in the refrigerator for 30 minutes — it will dissolve.

5. Verify: The solution should be perfectly clear and colorless. Cloudiness, particles, or color indicate contamination or degradation — do not use.

6. Refrigerate: Store at 2–8°C immediately. Mark the vial with: date reconstituted, BAC water volume added, and concentration.

Common Reconstitution Mistakes

Spraying water directly onto the powder: High-pressure streams can denature the peptide through shear stress. Always aim at the vial wall and let the water run down onto the cake.

Shaking the vial: Vigorous shaking introduces air bubbles (oxidation risk) and can cause aggregation through mechanical stress. Gentle swirling only.

Using sterile water for multi-use vials: Sterile water has no preservative. Once punctured, it's vulnerable to bacterial contamination. BAC water (with benzyl alcohol preservative) is correct for any vial you'll draw from more than once.

Not labeling the vial: Two weeks from now, you won't remember how much water you added. Label every vial with: peptide name, vial size, BAC water volume, concentration, and reconstitution date.

Room temperature storage: See our degradation science guide — leaving reconstituted peptides at room temperature accelerates every degradation pathway simultaneously.

Where to Source Peptides and Supplies

Frequently Asked Questions

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