01 What it is
Most peptides arrive as a dry powder because they keep far better that way. To use one, you add water. Plain sterile water is meant for a single use, but every time a needle goes through the rubber stopper there is a small chance of bringing in bacteria. The 0.9% benzyl alcohol in BAC water stops bacteria from growing, which is why one mixed vial can safely last for weeks of doses.
02 Common uses
03 How it’s used
Draw the water with a fresh syringe and let it run slowly down the inside wall of the peptide vial. Never squirt it onto the powder. Swirl gently, don’t shake. 2ml is the standard amount for a 3ml vial, and up to 3ml makes a gentler, less stingy shot. Wipe the stopper with alcohol before every draw, store the bottle at room temperature away from light, and discard it 28 days after first opening or sooner if it turns cloudy. Pre-filled pens don’t need it.
Ask how much water to add for your vial, and what that means for the units you draw.
04 What to watch for
Use bacteriostatic water, not plain sterile water, for any vial you will draw from more than once. Don’t use it if it looks cloudy, has particles, or the seal was broken. A small number of people react to benzyl alcohol. It is not for use in newborns, and anyone pregnant should ask a doctor. Redness, warmth or swelling at an injection site that gets worse after 48 hours needs checking.
05 Evidence & status
Standard diluentNot a treatment. It is a standard pharmaceutical diluent used in clinics and hospitals.
In the US, Bacteriostatic Water for Injection, USP is a regulated pharmaceutical product.
06 FAQ
BAC water or sterile water?
For a vial you will draw from more than once, bacteriostatic. Plain sterile water has no preservative and is meant for a single use.
How much do I add?
2ml is standard for a 3ml peptide vial; anywhere from 2 to 3ml is fine. More water means fewer mg per unit, so redo the math in the calculator.
How long does an opened bottle last?
The usual rule for an opened multi-dose bottle is 28 days. Write the date on it when you first open it.
Educational information only — not medical advice. The Daily Stack does not sell or supply any products. Talk to a licensed healthcare professional about your own health decisions.