How Much Bacteriostatic Water to Add to Peptides?
The amount of bacteriostatic water (BAC water) you add determines your peptide concentration. There’s no single “correct” amount — choose a volume that makes your desired dose easy to measure on an insulin syringe.
The Simple Formula
Concentration = Peptide Amount ÷ BAC Water Volume
Example: 5mg peptide + 2mL BAC water = 2.5mg/mL (or 2,500mcg/mL).
Quick Reference by Vial Size
2mg vial: Add 1mL ? 2,000mcg/mL. Add 2mL ? 1,000mcg/mL. 5mg vial: Add 1mL ? 5,000mcg/mL. Add 2mL ? 2,500mcg/mL. 10mg vial: Add 1mL ? 10,000mcg/mL. Add 2mL ? 5,000mcg/mL.
How to Choose Your Volume
Work backward from your research dose. If you want 250mcg doses from a 5mg vial: Using 2mL ? 2,500mcg/mL ? 250mcg = 10 units (0.1mL). Clean, easy to measure. Using 1mL ? 5,000mcg/mL ? 250mcg = 5 units (0.05mL). Harder to measure accurately.
General Guidelines
Use enough BAC water to make your dose at least 5 units on the syringe (for measurement accuracy). Don’t add more than 3mL to a standard 3mL vial. Common volumes are 1mL or 2mL for most research peptides. See our reconstitution calculator for exact concentrations.
Important Notes
Always use bacteriostatic water (NOT sterile water or saline) — the 0.9% benzyl alcohol preservative prevents bacterial growth in multi-use vials. Add water slowly along the vial wall, never directly onto the peptide powder. Swirl gently, never shake.
Related Articles: How to Mix Peptides | Reconstitution Calculator | BAC Water Guide
For research use only. Shop research peptides and bacteriostatic water at Proxiva Labs.