Bacteriostatic vs Sterile vs Saline Water for Peptides
The quick comparison
| Water | What it is | Preservative? | Best for |
|---|---|---|---|
| Bacteriostatic water | Sterile water with 0.9% benzyl alcohol | Yes | Multi-dose vials when the product instructions specify it |
| Sterile water for injection | Sterile water, nothing added | No | Single use: mix and use immediately |
| Saline (0.9% sodium chloride) | Sterile salt solution | Plain: no | Mostly IV dilution; not the usual peptide diluent |
Bacteriostatic water: preserved sterile water
Bacteriostatic water is sterile water with 0.9% benzyl alcohol as a preservative, which slows bacterial growth after the vial is punctured. It's often specified for multi-dose use, but it doesn't replace your product's directions. Follow its label and your instructions for discard timing. How long the mixed product keeps varies by medicine.
Sterile water: single use only
Sterile water for injection has nothing added. With no preservative, an opened vial is single use, and leftovers are discarded. After mixing, follow the product's storage instructions, and if there are none, don't store or reuse it.
Benzyl alcohol isn't suitable for newborns, and a few people are sensitive to it. Their instructions may specify sterile water or another diluent instead, and the mixed vial is then usually single use.
Saline: not the usual choice
Saline is 0.9% sodium chloride, a sterile salt solution used mainly for intravenous fluids and dilution. Plain saline has no preservative, so it's single use once opened. A preserved version, bacteriostatic saline, exists. Use either only when your instructions name it.
Supplies
- 10mL bacteriostatic water vial: preserved sterile water, when your instructions specify it.
- 10mL syringe with an 18G draw needle: transfers diluent quickly where that size and gauge suit the vial. Avoid repeated punctures with a large needle, which damage the stopper.
- 0.5mL insulin syringes (31G, 6mm): for drawing each dose where this syringe suits your route and volume. Use a new one each time and never one syringe across vials.
- 70% isopropyl alcohol wipes (100-pack): swab every stopper.
Browse the full injection supplies range.
Frequently asked questions
Can I use sterile water instead of bacteriostatic water?
Only if your product information, prescriber or pharmacist specifies sterile water. It has no preservative, so treat it as single use once opened or mixed unless your instructions say otherwise.
A vial storage case keeps vials upright, cushioned and organised. It doesn't control temperature, so follow your product's temperature requirements separately.
Is saline OK for reconstituting peptides?
Only if your instructions specify it. Plain saline has no preservative and is single use once opened.
Why can't I just use tap or distilled water?
They aren't sterile, so they can carry bacteria into the injection.
Who should not use bacteriostatic water?
Newborns, and the few people sensitive to benzyl alcohol. Their instructions may specify sterile water or another diluent, usually single use.
Related guides
- How to reconstitute peptides with bacteriostatic water
- How long do reconstituted peptides last?
- Bacteriostatic water: what needle to use and how to draw it
This guide compares injection supplies and is not medical advice. Follow approved product information and your prescriber or pharmacist for your medicine.
