Bacteriostatic water is sterile water for injection with 0.9% benzyl alcohol as a preservative, which keeps a punctured vial usable for about four weeks.
What published studies and recent community write-ups report about amounts, timing and course length. 2 clinical and 4 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.
| Context | Dose | Frequency | Route | Course | Source |
|---|---|---|---|---|---|
| Clinical2 rows | |||||
| FDA label: multiple-dose diluent, 30 mL vialAdults and children other than neonates, as a vehicle for drugs that require dilution or dissolution before injection | 0.9% (9 mg/mL) benzyl alcohol in water for injection; some presentations carry 1.1% (11 mg/mL) | Repeated withdrawals from one vial with aseptic technique | Diluent for intravenous, intramuscular or subcutaneous drugs; never given on its own | Multiple-dose containerNot applicable | DailyMed, National Library of Medicine2026 |
| The label gives a pH of 5.7 (4.5 to 7.0) and states the preparation is designed solely for parenteral use after a drug has been added. It must be made approximately isotonic before use, is not for fluid replacement, is not for epidural or spinal anaesthesia, and must not be used in neonates because of benzyl alcohol toxicity. Animal studies cited on the label suggest an estimated intravenous dose of up to 30 mL could be given to an adult without toxic effect, while about 9 mL in a 6 kg infant could change blood pressure, which is the scale of the benzyl alcohol margin. | |||||
| UK summary of product characteristicsPatients receiving benzyl alcohol-preserved diluent, with specific limits for children under 3 and neonates | 9.45 mg/mL benzyl alcohol in 1 mL pre-filled syringes | As a diluent only | Diluent for injection | Not more than 1 week in children under 3 years unless necessaryNot applicable | electronic medicines compendium (emc)2026 |
| The UK label spells out the hazard behind the neonatal contraindication: intravenous benzyl alcohol has been associated with serious adverse events and death in infants, known as gasping syndrome, and the minimum toxic amount is not known. It also asks prescribers to consider the combined daily benzyl alcohol load from all sources in liver or kidney impairment and in pregnancy or breastfeeding, because accumulation can cause metabolic acidosis. For a peptide user the relevance is simply that the preservative is a drug with a dose, not an inert ingredient. | |||||
| Community-reported4 rows | |||||
| Community reconstitution guide: volume sets concentration | 1 mL per 5 mg vial gives 5 mg/mL; 2 mL per 5 mg vial gives 2.5 mg/mL | Once, at reconstitution | Injected slowly down the inside wall of the peptide vial, taking at least 30 seconds per mL | Use within 28 days of first punctureNot applicable | Community resource2026 |
| This 2026 guide describes the two most common conventions and the technique that goes with them: let the water trickle down the glass so it pools around the cake rather than hitting it, then swirl gently. It treats 28 days at 2 to 8 degrees as a firm deadline because there is no way to assess potency afterwards without laboratory testing, and notes that robust peptides such as BPC-157 probably outlast fragile growth hormone secretagogues. The volume is a measurement choice, not a dose: more water means a lower concentration and a larger draw for the same amount. | |||||
| Community guide: ratio math and common mistakes | Peptide mass in mg divided by water volume in mL equals concentration in mg/mL; 2 mL per 5 mg vial is the math-friendly default | Once, at reconstitution | Down the vial wall, swirled not shaken | 28 days, described as the preservative's in-use window rather than a peptide stability figureNot applicable | Community resource2026 |
| This guide makes a point the others often miss: the 28-day figure comes from the bacteriostatic preservative's in-use window under refrigeration, not from stability data on any particular peptide, so actual stability varies by compound. It explains why shaking is discouraged, citing formulation studies in which air-liquid interfaces and shear promote protein unfolding and aggregation, and says to discard any solution that turns cloudy, discolours or develops particles. | |||||
| Community guide: volumes for small doses and storage by peptide class | 2-5 mL per 5 mg vial (1-2.5 mg/mL) when doses of 100-300 mcg need to be measured | Once, at reconstitution | Released down the inner glass wall, then swirled; full dissolution expected within 60 seconds | About 30 days refrigerated for most synthetic peptides; about 14 days for recombinant proteins, oxytocin, NAD+ and other oxidation-prone compoundsNot applicable | Community resource2026 |
| The worked example is the one most calculators reproduce: 5 mg in 2 mL is 2.5 mg/mL, so 10 units on a U-100 syringe is 0.1 mL and 250 mcg. The guide's three rules cover most problems: use bacteriostatic rather than sterile water for anything stored and drawn from repeatedly, add the diluent slowly down the wall, and never shake. It also says a solution still cloudy after five minutes of swirling should be discarded rather than used. | |||||
| Community guide: bacteriostatic versus sterile water shelf life | Water volume in mL equals peptide amount in mg divided by the desired concentration in mg/mL; 5 mg in 2 mL gives 2.5 mg/mL | Once, at reconstitution | Needle at about 45 degrees so the liquid runs down the wall | About 28 days refrigerated with bacteriostatic water; about 24 hours with plain sterile waterNot applicable | Community resource2026 |
| This guide's storage table is the clearest statement of why the preservative matters: a vial reconstituted with bacteriostatic water is described as usable for roughly 28 days in the refrigerator, while the same vial made up with preservative-free sterile water is given 24 hours. Unopened lyophilised powder is listed at 24 to 36 months frozen. Dissolution is expected within 30 to 60 seconds of gentle rotation. | |||||
Both stoppers are wiped with alcohol, the calculated volume is drawn, and the water is released slowly down the inside wall of the peptide vial rather than onto the powder. The vial is swirled or rolled, never shaken, and most lyophilised peptides clear within one to two minutes.
The vial is labelled with concentration and date, kept at 2 to 8 degrees and protected from light. The 28-day convention is the preservative's in-use window; oxidation-prone compounds are often given about 14 days instead, and anything that turns cloudy is discarded.
The diluent is also a multiple-dose vial that is punctured repeatedly, so the same aseptic technique applies to it, and the label's benzyl alcohol warnings travel with every millilitre drawn from it.
Plus 5 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.
Bacteriostatic water is sterile water for injection with 0.9% benzyl alcohol as a preservative, which keeps a punctured vial usable for about four weeks. It is supplied in 30 mL multiple-dose vials so that repeated withdrawals can be made to dissolve or dilute drugs for injection, and that preservative is why it is the standard diluent for lyophilised peptide vials where plain sterile water is a single-use product. It is a licensed prescription product with its own label, which contraindicates it in newborns and says it must be made approximately isotonic before use, and there is no single PubChem record because it is a two-ingredient formulation rather than a compound.
These themes describe recurring questions in published research. They are not claims of effectiveness or recommendations for use.
Diluents and buffers a lyophilised vial is dissolved in.
The label gives a pH of 5.7 (4.5 to 7.0) and states the preparation is designed solely for parenteral use after a drug has been added. It must be made approximately isotonic before use, is not for fluid replacement, is.
The UK label spells out the hazard behind the neonatal contraindication: intravenous benzyl alcohol has been associated with serious adverse events and death in infants, known as gasping syndrome, and the minimum toxic.
This 2026 guide describes the two most common conventions and the technique that goes with them: let the water trickle down the glass so it pools around the cake rather than hitting it, then swirl gently. It treats 28.
This guide makes a point the others often miss: the 28-day figure comes from the bacteriostatic preservative's in-use window under refrigeration, not from stability data on any particular peptide, so actual stability.
The worked example is the one most calculators reproduce: 5 mg in 2 mL is 2.5 mg/mL, so 10 units on a U-100 syringe is 0.1 mL and 250 mcg. The guide's three rules cover most problems: use bacteriostatic rather than.
Study models remain visible so laboratory and animal findings are not mistaken for established human outcomes.
2 protocol rows on this page come from human trials, trial registrations, regulator labels or reviews of human data. Approval status and populations are stated per row.
4 rows record what blogs, vendor write-ups or forums describe for Bacteriostatic Water. None has been verified against primary literature.
5 curated references, each with its journal, year and study model, plus 5 community resources reported but not linked.