Short answer: bacteriostatic water and sterile water are both sterile, pharmaceutical-grade water. The difference is one ingredient: bacteriostatic water contains 0.9% benzyl alcohol, a preservative that stops bacteria from multiplying. That single difference changes everything about how you use, store and reuse a vial. Sterile water is single-use. Bacteriostatic water is made for repeated withdrawals and is the standard diluent for reconstituting multi-use laboratory peptide vials. Below: the full comparison, how long each one lasts, the “reconstitution solution” confusion, and where to find it in Canada.
Here is a fun fact from Google’s own suggestions: when people type “is bacteriostatic water the same as,” Google finishes the sentence with sterile water, reconstitution solution, saline, bacteriostatic sodium chloride, deionized water. Five different guesses. It is one of the most confused products in the whole research-peptide world, which is surprising for something that is, essentially, water. Let’s clear it up for good.
Bacteriostatic water vs sterile water: side by side
| Bacteriostatic water | Sterile water | |
|---|---|---|
| What is in it | Sterile water + 0.9% benzyl alcohol (9 mg/mL) | Sterile water only |
| Preservative | Yes | No |
| Container type | Multiple-dose vial | Single-dose vial or ampoule |
| Repeated withdrawals | Designed for it | Not intended; discard after first use |
| After first puncture | Up to 28 days (standard pharmacy rule for multi-dose vials) | Use immediately |
| Storage (label) | Room temperature, 20–25 °C | Room temperature |
| Typical pH | About 5.7 (range 4.5–7.0) | Similar, slightly acidic |
| Label warning | Not for use in neonates (benzyl alcohol) | None related to preservative |
| Main lab use | Reconstituting multi-use vials | Single-use reconstitution, or compounds that cannot tolerate benzyl alcohol |
Both are sterile when sealed. The question is what happens after the stopper has been punctured. Every time a needle goes through a rubber septum, there is a small chance of introducing microorganisms. In sterile water, nothing stops them from growing. In bacteriostatic water, the benzyl alcohol keeps them from multiplying.
What benzyl alcohol actually does (and doesn’t)
“Bacteriostatic” means it stops bacteria from growing. It does not mean “bactericidal,” which would mean it kills them. That distinction matters:
- It is a safety margin against the small contamination risk of repeated punctures.
- It is not a way to rescue a contaminated vial, and it does not make poor technique safe.
- It does not protect against everything. Some organisms and fungi are less affected.
Benzyl alcohol also comes with its own caution. The manufacturer’s label carries a boxed warning, “Not for use in neonates,” because benzyl alcohol has been associated with serious toxicity in newborns. The label also notes that bacteriostatic water is a diluent: it must be combined with a solute and made approximately isotonic, not used on its own.
Saline, bacteriostatic saline and “reconstitution solution”
| Product | What it is | Key point |
|---|---|---|
| Bacteriostatic water | Water + 0.9% benzyl alcohol | The standard for multi-use peptide vials |
| Sterile water for injection | Water only | Single use |
| Normal saline (0.9% NaCl) | Salt water, matches body fluids | Usually no preservative; the salt can affect some peptides’ solubility |
| Bacteriostatic sodium chloride | 0.9% saline + 0.9% benzyl alcohol | Multi-use saline; a different product from bacteriostatic water |
| “Reconstitution solution” | Not a standard pharmaceutical name | Could be bacteriostatic water, sterile water or something else. Read the composition. |
| Distilled or deionized water | Purified but not sterile | Not a substitute for sterile diluents |
“Reconstitution solution” deserves a special warning. It is a name some sellers use online, partly because marketplaces restrict listings for injectable products. Sometimes it is exactly bacteriostatic water under another name. Sometimes the composition is vague. Rule of thumb: if the label does not state the exact contents, including the benzyl alcohol percentage, you do not know what you have.
Does bacteriostatic water expire?
Yes, in two different ways, and people mix them up:
- Unopened: the expiry date printed on the vial applies, as long as it has been stored as labelled.
- Once punctured: a separate clock starts. The widely used pharmacy standard for multiple-dose vials (USP chapter <797>) is 28 days after first puncture, unless the manufacturer specifies otherwise. After that, discard it, even if there is liquid left and it still looks clear.
Write the date on the vial the first time you puncture it. It is the simplest habit in the whole lab and the one most often skipped.
Important distinction: the 28-day rule is about the diluent vial itself. A peptide you reconstitute with it has its own stability window, which depends on the peptide and is often shorter. See how to store peptides.
Does it need to be refrigerated?
Not according to the label. The manufacturer’s storage instruction for bacteriostatic water is controlled room temperature, 20–25 °C. Many labs choose to refrigerate an opened vial anyway to slow any microbial growth, and that is a reasonable practice. What you should avoid:
- Freezing. Freezing is not part of the labelled storage and expanding ice can stress the glass and the stopper seal.
- Heat and direct sunlight, such as a car in summer or a windowsill.
- Leaving it uncapped or with a damaged stopper.
Why peptide labs use bacteriostatic water
Most research peptides are supplied as lyophilized (freeze-dried) powder and must be dissolved before use. A single vial is usually drawn from many times over days or weeks. That is exactly the situation bacteriostatic water was designed for. Sterile water works for a vial that will be used all at once, or for the rare compound that is incompatible with benzyl alcohol.
The step-by-step technique, including concentration tables, is in our peptide reconstitution guide.
Where to buy bacteriostatic water in Canada
“Where to buy bacteriostatic water Canada” and “bacteriostatic water Shoppers Drug Mart” are both common searches. Here is the honest picture:
- Pharmacies. Pfizer’s Bacteriostatic Water for Injection USP carries a Health Canada DIN (00038202). It is listed as an “ethical” product, meaning it is a non-prescription drug that is marketed mainly to health professionals. In practice, many pharmacies do not stock it on the shelf and may need to order it, and individual pharmacists can decide whether to sell it.
- Shortages happen. Health Canada’s drug shortage database has recorded supply disruptions for it, most recently a short shortage in late 2025 due to a manufacturing disruption.
- Medical and lab suppliers sell it to clinics and institutions.
- Research suppliers. Most research-peptide suppliers, including TrueLabs, sell bacteriostatic water for laboratory reconstitution, so it arrives with the peptide order from inside Canada.
Whatever the source, check three things: the composition is stated (sterile water + 0.9% benzyl alcohol), the vial is sealed with an intact crimp cap, and there is a lot number and expiry date.
See TrueLabs bacteriostatic water →
Frequently asked questions
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Is bacteriostatic water the same as sterile water?
No. Both are sterile, but bacteriostatic water contains 0.9% benzyl alcohol as a preservative and is made for multiple withdrawals. Sterile water has no preservative and is meant for single use.
How long does bacteriostatic water last after opening?
The common pharmacy standard for multiple-dose vials is 28 days after first puncture, unless the manufacturer specifies otherwise. Unopened, it lasts until the printed expiry date.
Does bacteriostatic water need to be refrigerated?
No. The label specifies room temperature, 20–25 °C. Many labs refrigerate opened vials as an extra precaution. Avoid freezing and heat.
Is bacteriostatic water the same as reconstitution solution?
Sometimes. “Reconstitution solution” is not a standard pharmaceutical name, so the product could be bacteriostatic water, sterile water or something else. Check that the label states the exact composition.
Is bacteriostatic water the same as saline?
No. Saline is 0.9% sodium chloride. Bacteriostatic water contains no salt. Bacteriostatic sodium chloride is a separate product that combines saline with benzyl alcohol.
Do you need a prescription for bacteriostatic water in Canada?
Pfizer’s product is listed as an “ethical” non-prescription drug in Canada, but it is marketed to health professionals, so pharmacies may not stock it and may decide case by case. Research suppliers also sell it for laboratory use.
Can you use distilled water instead?
No. Distilled or deionized water is purified but not sterile, and it contains no preservative.
Related reading
- How long does reconstituted BPC-157 last?
- How to reconstitute peptides: the complete lab guide
- How to store peptides: 6 mistakes that ruin research
- How to read a peptide COA
References
- Pfizer (Hospira). Bacteriostatic Water for Injection, USP: prescribing information. Pfizer
- Pfizer (Hospira). Bacteriostatic Sodium Chloride Injection, USP: prescribing information. Pfizer
- United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding: Sterile Preparations (multiple-dose container beyond-use dating). USP
- Health Canada Drug Shortages Canada. Bacteriostatic Water for Injection USP, DIN 00038202, shortage report (resolved December 2025). Drug Shortages Canada
All TrueLabs products are sold for in vitro and laboratory research use only. They are not intended for human or veterinary use, and nothing in this article is medical advice.