BAC Water
How Much Bacteriostatic Water to Add
There's no single "correct" amount of bacteriostatic water; any volume works mathematically. What it changes is your concentration, and therefore how big each draw is. Here's how to pick a volume that's easy to measure accurately.
The water volume is a choice, not a rule
The peptide amount in the vial is fixed. Adding more or less water doesn't add or remove peptide; it only spreads the same peptide across more or less liquid. So the question isn't "how much water is required," it's "what concentration makes my doses easy to measure?"
The trade-off
- More water → lower concentration → you draw a larger volume per dose. Easier to measure precisely, but you use up the vial's liquid faster.
- Less water → higher concentration → you draw a smaller volume per dose. Stretches further, but tiny draws are harder to read accurately.
A good target is a draw that lands somewhere readable on your syringe: not so small that a single unit is hard to hit, and not so large that you're drawing most of the barrel each time.
Quick reference: a 10 mg vial
Here's how water volume affects a 10 mg vial and the draw for a 0.5 mg dose on a U-100 syringe:
| Water added | Concentration | Draw for 0.5 mg | Units (U-100) |
|---|---|---|---|
| 1 mL | 10 mg/mL | 0.05 mL | 5 |
| 2 mL | 5 mg/mL | 0.10 mL | 10 |
| 3 mL | 3.33 mg/mL | 0.15 mL | 15 |
| 5 mL | 2 mg/mL | 0.25 mL | 25 |
All four are equally "correct"; they just give you different unit marks to read. Many people pick a round number (like 1, 2, or 3 mL) so the resulting concentration is easy to remember.
Try different water volumes
Plug in a vial amount and a few water volumes to see which gives you the cleanest unit number to draw.
Open the free calculatorDon't forget the vial's capacity
Add only as much water as the vial can comfortably hold, and keep sterile technique. The chart above is about the math; always follow the handling and storage instructions for your specific product and your clinician's guidance.
This guide is for calculation and educational purposes only and is not medical advice. It does not recommend any peptide, dose, or protocol. Always consult a qualified clinician and follow sterile technique and product storage instructions.