PRODUCTS SOLD ON PEPTIDESLABIRELAND.COM ARE FOR RESEARCH PURPOSES ONLY AND ARE NOT FOR HUMAN OR VETERINARY USE.
Fast Ireland delivery — dispatched to Dublin, Cork, Galway, Limerick and nationwide.
PRODUCTS SOLD ON PEPTIDESLABIRELAND.COM ARE FOR RESEARCH PURPOSES ONLY AND ARE NOT FOR HUMAN OR VETERINARY USE.
Fast Ireland delivery — dispatched to Dublin, Cork, Galway, Limerick and nationwide.
By the Peptides Lab Ireland research team · Updated July 2026 · Research use only
It is the least glamorous item in any peptide order and the one most likely to hold up your work if you forget it. Bacteriostatic water is what you reconstitute a lyophilised peptide with, and Irish researchers ask us two things about it constantly: where do I actually get it, and can I just pick it up in a pharmacy? This covers both, along with the part that trips people up — the difference between bacteriostatic water and the other sterile waters you will see listed.
Usually not off the shelf. Bacteriostatic water is not a general over-the-counter product in Irish pharmacies the way saline sachets or plasters are. Some pharmacies can order it in, but it is treated as a pharmacy-supply item rather than front-of-shop stock, and availability is inconsistent from branch to branch. For research groups that need it reliably and in known quantities, ordering it alongside the peptides it will be used with is simpler and avoids the situation where the compound arrives and the diluent does not. That is the practical reason most labs source both from the same supplier.
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol. The benzyl alcohol is a preservative — it stops bacterial growth in the vial, which is what lets you draw from the same container more than once over a period of weeks rather than discarding it after a single use. That single feature is the whole point of it for peptide work, where a reconstituted vial is typically used across multiple sessions.
The three waters people confuse are not interchangeable, and using the wrong one is a common early mistake.
| Type | Preservative | Reuse window | Typical role |
|---|---|---|---|
| Bacteriostatic water | 0.9% benzyl alcohol | ~28 days multi-draw | Standard peptide diluent |
| Sterile water for injection | None | Single use | One-off preparations |
| Water for injection (WFI) | None | Single use | Bulk/manufacturing prep |
For most peptide protocols the multi-draw window is exactly why bacteriostatic water is the default. Where a peptide is known to interact poorly with benzyl alcohol, a preservative-free option is used instead and prepared fresh each time — but that is the exception, not the rule.
A little goes a long way. A 10 mg vial is usually reconstituted with 1–2 ml, so a single 10 ml container of bacteriostatic water covers a good run of vials. The reason to keep a spare is preservative life rather than volume: once opened, a bacteriostatic vial is generally considered good for around 28 days, so buying one enormous container for occasional use is a false economy. Match your bac water quantity to how quickly your group actually gets through it.
Unopened, bacteriostatic water is fine at room temperature and does not need refrigerating. Once you have pierced the stopper, store it in the fridge at 2–8 °C, keep it out of direct light, and note the date you opened it. The peptide you reconstitute with it has its own, usually shorter, stability window — our peptide storage lifetime guide covers how long different compounds actually last once mixed.
The technique matters as much as the water. Add the bacteriostatic water slowly, aiming it against the inside wall of the vial rather than blasting it onto the peptide, then let the powder dissolve on its own instead of shaking. Peptides are more fragile than they look and vigorous agitation can degrade them. The full method, including working out the right diluent volume for your target concentration, is in our reconstitution guide.
Peptides Lab Ireland stocks bacteriostatic water and dispatches it from Irish stock alongside your peptides to Dublin, Cork, Galway, Limerick and nationwide, so the diluent and the compound arrive together. You can see it on the bacteriostatic water product page. If you are new to the process, start with our guide to buying research peptides in Ireland.
For laboratory research use only. Not intended for human or veterinary use.
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