Bacteriostatic water vs sterile water
You can distinguish bacteriostatic water from sterile water for injection by their preservatives, single-dose versus multiple-dose use and the 28-day limit.
- The benzyl alcohol used in bac water
- 0.9%
- Sterile water's preservative
- No
- Once you open bac water
- 28 days
- A vial of sterile water
- 1 use
With bacteriostatic water vs sterile water, everything depends on 1 ingredient: 0.9% benzyl alcohol. That preservative keeps a bac water vial usable for 28 days; plain sterile water permits only 1 use. At room temperature, both are sterile products used to mix injectable drugs: 68 to 77 F equals 20 to 25 C.
| Bacteriostatic water | Sterile water for injection | |
|---|---|---|
| Preservative | 0.9% benzyl alcohol (9 mg/mL) | No preservative |
| Vial type | Multiple-dose vial | Single-dose vial |
| After the first needle | Throw it away within 28 days (CDC), except when the manufacturer says otherwise. | Use once, discard the rest |
| Label vial sizes | 20 mL and 30 mL (Hospira) | 10 mL (Fresenius Kabi) |
| Newborns | Not for use in neonates | The choice for drugs given to newborns |
| Manufacturer |  Hospira, a Pfizer company | Fresenius Kabi |
Bacteriostatic water vs sterile water: the one real difference
According to the Hospira FDA label, Bacteriostatic Water for Injection, USP is sterile water containing 0.9% benzyl alcohol, or 9 mg per mL. After a needle puncture, benzyl alcohol stops bacterial growth, so the container carries a multiple-dose label.
According to the Fresenius Kabi FDA label, Sterile Water for Injection, USP contains no preservative at all. Each label warns that injecting either water into a vein without dissolved drug may cause hemolysis, meaning the bursting of red blood cells.
Sterile water for injection: use once, then discard
Without a preservative to stop germs, plain sterile water is supplied only in single-dose containers. After pushing your needle in 1 time, take the water you need and discard whatever remains in the bottle.
Fresenius Kabi also directs you to mix the drug thoroughly and then use the solution right away. You shouldn't store a solution mixed with plain sterile water unless the drug manufacturer specifically allows it.
Sizes and brands of sterile water vials
According to the Fresenius Kabi FDA label in our data, Sterile Water for Injection, USP comes in a 10 mL single-dose vial. According to the Hospira FDA label, preserved water comes in multiple-dose vials of 20 mL and 30 mL; peptide shops also list 10 mL vials. At 68 to 77 F, equivalent to 20 to 25 C, both kinds remain suitable for storage while unopened.
What your vial needs you to use
When you mix a powdered vial, the liquid is selected by your drug label or prescriber; your prescriber also determines each dose. Because you inject them right after mixing, some daily drugs use plain sterile water. The daily vial in the Egrifta SV kit comes with Sterile Water for Injection. Some drugs, including Novarel hCG, can remain refrigerated for up to 30 days after mixing with 0.9% benzyl alcohol water.
The FDA boxed warning calls newborn babies neonates, and there is no choice between the 2 waters for them. Benzyl alcohol is linked with toxicity in newborns; for mixing drugs for newborns, you should use only preservative-free sterile water for injection.
Mixing a vial that you will use over weeks
With several weeks of doses in a medication vial, each needle entry needs bacterial protection. The CDC guidance says to mark a multiple-dose vial with its first-puncture date and throw it away within 28 days. Keeping the vial beyond that period is allowed only when the manufacturer provides a different date. Plain sterile water can't keep a multi-week vial safe unless the drug manufacturer explicitly tells you to store it that way.
Questions people often ask
Does sterile water for injection come in a bacteriostatic form?
Bac water is already a bacteriostatic sterile water for injection. The official label identifies the product as Bacteriostatic Water for Injection, USP, meaning sterile water for injection plus 0.9% benzyl alcohol.
For peptides, can I substitute sterile water for bac water?
No FDA label exists for research peptides such as BPC-157. Only your drug label or prescriber can identify the right liquid for your vial. Because plain sterile water has no preservative, its label directs prompt use of the mixed drug unless the drug manufacturer states otherwise.
Does distilled water match sterile water?
No. Never inject distilled water taken from a grocery store or pharmacy shelf. Made and sealed for injection under strict medical sterility rules, Sterile Water for Injection, USP differs from bottled distilled water, which isn't made for injection.