Does it need refrigerating?
No. The label gives room temperature, 20 to 25 °C. A peptide dissolved in it is a different matter. Storage →
A label-based guide
Bac water for peptides
Bac water is sterile water with 0.9% benzyl alcohol added. The alcohol lets a vial be punctured again and again for up to 28 days, which is why it is the usual liquid for dissolving freeze-dried peptides. Nothing in the vial is made for peptides specifically.
From the label: a diluent, for diluting or dissolving other products only. Not for use in neonates. Given intravenously without a solute it may cause hemolysis. Where the product being prepared has its own instructions, those come first.
Quick answers
The questions people ask first
How long does an opened vial last?
28 days from the first puncture under USP and CDC guidance, and never past the printed expiry. Shelf life →
Can sterile water be used instead?
For a single draw, yes. It has no preservative, so a vial made up with it is single-use. Comparison →
How much goes in the peptide vial?
The volume is a choice. It sets the concentration, and the calculator shows what each choice gives.
What it is
What is bac water for peptides?
It is Bacteriostatic Water for Injection, USP: sterile, nonpyrogenic water containing 9 mg of benzyl alcohol per mL. “For peptides” describes the use, not a different product. The same vial is sold to pharmacies for diluting injectable medicines.
Freeze-dried (lyophilized) peptides ship as a powder or a small cake at the bottom of a sealed vial. To use one, a measured volume of liquid goes in through the stopper and the powder dissolves. Because that vial then gets drawn from many times, the liquid needs a preservative. Plain sterile water has none.
You will also see it listed as “peptide water”, “BAC water” and “reconstitution solution”. Some of those listings are bacteriostatic water and some are not. The ingredient line on the vial settles it: 0.9% benzyl alcohol, or 9 mg/mL, in sterile water. If benzyl alcohol is missing, the vial is sterile water.
▣Printed on a genuine label
- “Bacteriostatic Water for Injection, USP”
- 0.9% benzyl alcohol (9 mg/mL)
- Multiple-dose vial
- “NOT FOR USE IN NEONATES”
- Store at 20 to 25 °C (68 to 77 °F)
- Lot number and expiry date
- “Rx only” on FDA-listed products
Commonly confused
Bac water, sterile water and reconstitution solution
Three names that get used as if they were one product.
Bac waterSterile water
Preservative0.9% benzyl alcoholNone
VialMultiple-doseSingle-dose
After first punctureUp to 28 daysUnused portion discarded
NeonatesNot usedDepends on the product
“Reconstitution solution” is the odd one out. It describes a job, not a formula, so a vial sold under that name can be either of the two columns above, or saline. How to tell which →
Shelf life
How long it lasts
A sealed vial lasts until the expiry on its label. The day a needle first goes through the stopper, a second clock starts: 28 days for a multiple-dose vial under USP ⟨797⟩ and CDC guidance, unless the manufacturer gives a different period.
Size and that clock are linked. A 30 mL vial costs less per mL, but only the volume used inside 28 days is worth anything.
Storage and shelf life →▣Dates that apply
- Sealed: printed expiry date
- Opened: 28 days, capped by the expiry
- Mixed with a peptide: the peptide’s own limits
Guides
More on bac water for peptides
Peptide reconstitution calculator
Vial strength, water volume and syringe size in; concentration and syringe units out.
How to reconstitute peptides
The steps in order, from checking both vials to labelling the finished one.
Bac water vs sterile water for peptides
One ingredient apart, and what that changes.
How long does bac water last?
Expiry, the 28 days after opening, and refrigeration.
Where to buy bac water for peptides
Online suppliers, pharmacies and marketplaces, with what each one sells.
Reconstitution solution vs bacteriostatic water
When the two names describe the same vial.
FAQ
Frequently asked questions
Is bac water the same as bacteriostatic water?
Yes. “Bac water” is short for bacteriostatic water.
Is there a special bac water for peptides?
No. Any vial labelled Bacteriostatic Water for Injection with 0.9% benzyl alcohol is the same product. The words “for peptides” on a listing add nothing to what is in it.
Can every peptide be dissolved in bacteriostatic water?
Not every one. A few are sold with a different diluent named, such as dilute acetic acid. Most research peptides come with no reconstitution instructions at all, and for those the label cannot answer the question.
Do you need a prescription for bacteriostatic water?
Pharmacies dispense it on prescription, because FDA-listed vials carry “Rx only”. Online suppliers sell it without one. See where to buy.
Does bacteriostatic water make a peptide safe to use?
No. It is the liquid, nothing more. It does not test, purify or sterilize what is dissolved in it.
Is benzyl alcohol the same as rubbing alcohol?
No. Rubbing alcohol is isopropyl or ethyl alcohol. Benzyl alcohol is an aromatic alcohol used as a preservative, here at 0.9%.
Buying