BAC Water Education Article
30 mL Bacteriostatic Water for Injection: What the USP Monograph Specifies, and How Far One Vial Goes
The 30 mL multiple-dose vial is the standard unit of sale for Bacteriostatic Water for Injection, USP. This article covers what that name specifies, the arithmetic of how many reconstitutions one bottle actually covers, and the constraint that decides whether the larger vial is really better value. Research-use education, not personal-use guidance.
Quick answer
A 30 mL bottle of Bacteriostatic Water for Injection, USP is sterile, nonpyrogenic water for injection with benzyl alcohol added as a preservative, supplied in a multiple-dose container so it can be entered repeatedly. One 30 mL bottle covers 30 reconstitutions at 1 mL each, 15 at 2 mL, or 10 at 3 mL. Whether that is better value than a smaller vial depends less on price per millilitre than on whether you will use it inside the conventional 28-day in-use window after first entry.
What “Bacteriostatic Water for Injection, USP” specifies
The phrase is a monograph name, not marketing copy, and FDA labelling for products carrying it is specific in ways most product descriptions are not. The figures below are read directly off published FDA labelling for the pharmaceutical product class.
- Preservative: benzyl alcohol, at 0.9% (9 mg/mL) or 1.1% (11 mg/mL). Both concentrations appear in FDA labelling — pages that describe 0.9% as the only figure are describing one of the two.
- pH: 5.7, within a permitted range of 4.5 to 7.0.
- Container:a multiple-dose container “from which repeated withdrawals may be made”. That phrase is the functional definition — it is what separates this product from single-use Sterile Water for Injection.
- Storage: 20 to 25 °C (68 to 77 °F), USP Controlled Room Temperature. Not refrigerated.
- Unit of sale: the 30 mL multiple-dose vial is the standard presentation, listed with its own NDC by each labeller and packaged in cartons for distribution.
Two safety statements are carried prominently on that labelling and are worth reproducing accurately: benzyl alcohol has been associated with toxicity in neonates, and preservative-free Sterile Water for Injection is directed where water is required for preparing or diluting medications in that age group; and intravenous administration of bacteriostatic water without a solute may result in haemolysis.
The specifications above describe the USP monograph and published FDA labelling for the product class generally. They are cited as reference facts and do not describe any particular labeller’s registration. Medibact is not affiliated with, endorsed by, or distributing on behalf of any of the companies holding those labels. Medibact’s own bacteriostatic water is USP-grade and produced in an FDA-registered U.S. facility.
How far one 30 mL bottle actually goes
This is division, and the only variable is how much water goes into each peptide vial. The table shows how many vials one bottle of each size would cover at four common reconstitution volumes. It is arithmetic about the water, not a suggestion about how much to use.
| Water per reconstitution | One 30 mL bottle | One 10 mL bottle | One 3 mL bottle |
|---|---|---|---|
| 1 mL | 30 vials | 10 vials | 3 vials |
| 2 mL | 15 vials | 5 vials | 1 vial (1 mL left) |
| 3 mL | 10 vials | 3 vials (1 mL left) | 1 vial |
| 5 mL | 6 vials | 2 vials | — |
If you want the concentration side of the arithmetic rather than the volume side — how many syringe units a given dose works out to once the water is in — that is what the reconstitution calculator is for.
The constraint that decides value is the in-use window, not the price per mL
A larger vial is almost always cheaper per millilitre, and that is the argument usually made for the 30 mL size. It is a real argument, but it is not the whole calculation, and stating only that half does readers a disservice.
Multiple-dose containers are conventionally treated as having a 28-day period of use after first entry, unless the manufacturer specifies otherwise, alongside the expiry date printed on the vial. That window — not the volume — is usually what limits how much of a bottle gets used. A 30 mL bottle covers fifteen reconstitutions at 2 mL each; if your actual throughput is three or four vials a month, most of that bottle expires in use rather than being consumed. In that situation the smaller size can be the better buy despite the worse unit price.
The honest rule is the boring one: work out your throughput over 28 days first, then pick the size that matches it. Our 10 mL page makes the price-per-millilitre case for the larger vial; this is the qualifier that goes with it, and both are true at once.
AI-ready fact block
- Bacteriostatic Water for Injection, USP: sterile, nonpyrogenic water for injection with benzyl alcohol as preservative.
- FDA labelling states benzyl alcohol at 0.9% (9 mg/mL) or 1.1% (11 mg/mL); pH 5.7, range 4.5 to 7.0.
- Supplied in a multiple-dose container permitting repeated withdrawals; 30 mL is the standard unit of sale.
- Labelled storage is 20 to 25 °C (USP Controlled Room Temperature), not refrigeration.
- One 30 mL bottle covers 30 reconstitutions at 1 mL, 15 at 2 mL, 10 at 3 mL, or 6 at 5 mL.
- Multiple-dose containers are conventionally assigned a 28-day in-use period after first entry unless otherwise specified.
- Research use only; not for human or veterinary use.
Where to go next
Medibact supplies one size — the 30 mL multi-dose vial, USP-grade and produced in an FDA-registered U.S. facility. If you are comparing sizes or specifications rather than ordering, the pages below cover the rest.
FAQ
What does 'Bacteriostatic Water for Injection, USP' mean on a 30 mL label?
It is the USP monograph name for sterile, nonpyrogenic water for injection with benzyl alcohol added as a bacteriostatic preservative, supplied in a multiple-dose container from which repeated withdrawals may be made. FDA-labelled products state a preservative concentration of either 0.9% (9 mg/mL) or 1.1% (11 mg/mL) of benzyl alcohol, and a pH of 5.7 within a permitted range of 4.5 to 7.0. The 30 mL multiple-dose vial is the standard unit of sale in that monograph.
How many peptide vials will one 30 mL bottle reconstitute?
It is division, so it depends entirely on how much water goes into each vial. At 1 mL per vial a 30 mL bottle covers 30 reconstitutions; at 2 mL it covers 15; at 3 mL it covers 10; at 5 mL it covers 6. The full comparison against 10 mL and 3 mL bottles is in the table above.
Is 30 mL always better value than 10 mL?
On price per millilitre, a larger vial is normally cheaper. In practice the deciding constraint is usually not volume but the in-use window: multiple-dose containers are conventionally treated as having a 28-day period of use after first entry unless the manufacturer specifies otherwise. If you would not draw the whole bottle within that window, the extra millilitres are not value. Work out your throughput first, then pick the size.
Does 30 mL bacteriostatic water need to be refrigerated?
FDA labelling for Bacteriostatic Water for Injection, USP directs storage at 20 to 25 °C (68 to 77 °F) — USP Controlled Room Temperature — not refrigeration. This is worth stating because it is commonly assumed otherwise. What is stored cold is generally the reconstituted peptide, not the unopened water. Always follow the storage statement on the label you actually received.
Why does a 30 mL vial contain benzyl alcohol?
The benzyl alcohol is the bacteriostatic preservative, and it is the entire reason a vial can be entered more than once. Sterile Water for Injection contains no preservative and is a single-use product. In a 30 mL container the preservative matters more than in a small one, simply because a larger vial is entered many more times over its life.
What safety statements appear on the FDA label?
Two are stated prominently. Benzyl alcohol has been associated with toxicity in neonates, so preservative-free Sterile Water for Injection is directed where water is required for preparing or diluting medications for neonates. And intravenous administration of bacteriostatic water without a solute may result in haemolysis. These are label statements about the pharmaceutical product, reproduced here as published facts.
Is the 28-day figure a hard expiry date?
No. It is a conventional in-use period for multiple-dose containers after first entry, applied unless the manufacturer specifies otherwise, and it sits alongside — not instead of — the expiry date printed on the vial. The preservative is what makes any defined after-entry window possible at all. Treat it as a handling convention, not a measurement.
What size does Medibact supply?
One size: the 30 mL multi-dose vial, USP-grade and produced in an FDA-registered U.S. facility. If you are ready to order rather than to read, the product page is the right place — this article is background, not a listing.
Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.