Definition: Sterile water for injection is sterile water with nothing added: no preservative, no antimicrobial agent and no buffer. It is used to dilute or dissolve drugs before injection. Because nothing stops bacteria from growing once the vial is opened, it comes in single-dose containers and the unused part is thrown away.
What the label says
The Hospira label states that it "contains no bacteriostat, antimicrobial agent or added buffer." It is "supplied only in single-dose containers" and the directions say "discard unused portion." Like bacteriostatic water, it is only for diluting or dissolving drugs; given into a vein without a dissolved drug, it may cause hemolysis.
Some labels require sterile water and nothing else. The Egrifta SV (tesamorelin) label says to use only the diluent provided, sterile water for injection, and to use the mixed solution right away.
Why it matters when you track doses
A vial mixed with sterile water has a much shorter usable life than one mixed with a preserved diluent, because each new needle puncture is a chance for contamination. If you log a vial mixed with sterile water, the mix date and time matter more, not less.
Egrifta SV, from the label
- The label mixes 1 vial (2 mg) with 0.5 mL of sterile water.
- Concentration: 2 mg ÷ 0.5 mL = 4 mg/mL.
- The label then gives 0.35 mL. Amount: 0.35 mL × 4 mg/mL = 1.4 mg.
- The leftover 0.15 mL (0.6 mg) is thrown away, as the label directs, because the mixed solution is not kept.
Common mix-ups
- Swapping in BAC water. When a label names sterile water, it is the diluent the product was tested with. Benzyl alcohol is not a neutral swap for every drug.
- Treating it as multi-dose. The label is single-dose. Keeping an opened vial for later draws is outside the label.
- Confusing it with sodium chloride. Saline (0.9% sodium chloride) is a different diluent. Some kits, like Pregnyl, use water with 0.56% sodium chloride and benzyl alcohol.
Read more on Dose Track: Bacteriostatic vs sterile water · How long mixed peptides last
General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
Is sterile water the same as bacteriostatic water?+
No. Sterile water for injection has no preservative and is single-dose. Bacteriostatic water has benzyl alcohol added so the vial can be punctured more than once.
Can I keep an opened vial of sterile water?+
The label says it is supplied only in single-dose containers and to discard the unused portion.
Why would a drug call for sterile water instead of BAC water?+
The label names the diluent the product was tested with. Egrifta SV, for example, says to use only the sterile water provided.