BAC Water Storage
Does Bacteriostatic Water Need to Be Refrigerated?
No. The approved labeling directs 20 to 25°C — USP Controlled Room Temperature — before the vial is opened and after. But most people asking mean the vial once it has been entered, and there the label and common practice diverge. This page keeps them apart and says where the familiar “2 to 8°C for 28 days” figure actually comes from. Research-use label education only.
The short answer
Every FDA-approved label checked carries one storage sentence: “Store at 20 to 25°C (68 to 77°F). [See USP Controlled Room Temperature.]” Hospira (DailyMed 87d6e9dc), HF Acquisition/HealthFirst (99b0ef9b) and US MedSource (ccadcf46) print it identically, and none mentions refrigeration, freezing, light protection or a discard period after entry. The 2 to 8°C convention is real, but it belongs to some reconstituted peptide products rather than to the water — see how to store peptides.
What the label actually says
Each row is printed on the labeling, or sourced to the standard that fills the gap where the labeling is silent. “Not mentioned” means a checked absence.
| Property | What the source states | Source |
|---|---|---|
| Storage condition | “Store at 20 to 25°C (68 to 77°F). [See USP Controlled Room Temperature.]” | All three labels |
| Refrigeration, freezing, light | Not mentioned — no requirement and no prohibition on any of them | All three labels |
| Discard period after entry | Not on the label; USP <797> §15.2 supplies it | USP <797> §15.2 |
| Container | “a multiple-dose container from which repeated withdrawals may be made” | Hospira |
| Inspection | “Do not use unless the solution is clear and seal intact.” | Hospira |
| Preservative | 0.9% (9 mg/mL) or 1.1% (11 mg/mL) benzyl alcohol | Hospira |
What “controlled room temperature” permits
The bracket does real work. By writing [See USP Controlled Room Temperature] the label incorporates the definition in USP General Chapter <659>, which is more forgiving than the bare numbers suggest: 20 to 25°C as the usual working environment, excursions between 15 and 30°C of the kind experienced in pharmacies, warehouses and shipping, a mean kinetic temperature no higher than 25°C, and transient spikes to 40°C permitted for up to 24 hours.
| Band | °C | °F | Standing |
|---|---|---|---|
| Controlled Room Temperature | 20 to 25 | 68 to 77 | The condition the label names |
| Permitted excursions | 15 to 30 | 59 to 86 | Allowed if mean kinetic temperature stays at or below 25 °C |
| Refrigerator | 2 to 8 | 36 to 46 | Not the labeled condition for this product |
One live caveat: the definition is moving. In Pharmacopeial Forum 52(4) USP proposed lowering the range to 15 to 25°C to align with Ph. Eur., JP and WHO, comments closing 30 September 2026. Pharmacopeial Forum sits behind registration, so that is reported here at second hand rather than read; the labels still print 20 to 25°C.
Can it go in the fridge anyway?
Nothing on the labeling prohibits it. This is water plus one dissolved organic liquid: benzyl alcohol, PubChem CID 244, C₇H₈O, 108.14 g/mol, systematically phenylmethanol, InChIKey WVDDGKGOMKODPV-UHFFFAOYSA-N. PubChem carries its aqueous solubility as 35,000 mg/L at 20°C, which puts the labeled concentrations at 26% and 31% of saturation.
That margin is real at 20°C, and worth being careful about extending downwards, because the trend runs the wrong way. The only two figures PubChem carries — 35,000 mg/L at 20°C and 42,900 mg/L at 25°C, both from the same HSDB compilation — get smaller as temperature drops, and PubChem publishes nothing at refrigerator temperature at all. Extrapolating a comfortable margin from two room-temperature points would be inventing data.
Nor does the trial literature fill the gap. Searched in September 2026, the ClinicalTrials.gov records mentioning bacteriostatic water at all are NCT00787761, NCT03487172, NCT00795678, NCT06919328, NCT07251608, NCT07386938, NCT04830722, NCT01580696 and NCT04996498 — each a study of something else, in which the water is a diluent or the vehicle control. None examines the water. Refrigeration here is unstudied rather than proven harmless, which is a different claim from either of the confident ones circulating.
What freezing and heat do
Freezing is the one direction with a mechanism you can point at. Water expands as it solidifies: USGS gives 0.99987 g/cm³ for liquid water at 0°C, NIST gives 0.9167 g/cm³ for ice at the same temperature, and the ratio makes the volume increase about 9.1% — consistent with USGS’s own statement that density falls by roughly nine percent on freezing. In a sealed vial with a crimped closure that is mechanical stress, and closure integrity is what keeps a multiple-dose vial usable across repeated entries.
Being straight about the sourcing, though: “do not freeze” is not printed on any of the three labels checked. Nor is “protect from light,” nor “avoid excessive heat.” Those phrases are near-universal on pages about this product and, on those three labels, they are inference rather than quotation. The qualifier matters: a fourth marketed label discussed further down does print “Protect from Light”, so the claim to make is about a specific label rather than about the product category. The inference also has a counter-example on the record: in NCT01580696, lyophilised peptide was suspended in bacteriostatic water for injection in cryovials and frozen deliberately, as part of the registered protocol. Heat is handled by the standard instead: a warm room or a delivery van sits inside the 15 to 30°C band, and what falls outside is sustained heat pushing the mean kinetic temperature above 25°C.
Storage after the vial has been opened
What the label requires. Nothing changes at first puncture. The storage sentence is unqualified, the labels state no in-use period, and the only direction attached to entry is technique: “Use aseptic technique for single or multiple entry and withdrawal from all containers.” A label that meant “refrigerate after opening” says so — as the two below do.
And one bacteriostatic water label does say so, which is the honest limit of the three checked above. A separately marketed product, TM BioWater (bacteriostatic water for injection, 30 mL multiple-dose, NDC 87597-003-30, listed in the FDA marketing category “unapproved drug other”, label version current as of 18 June 2026), prints all three of the things the Hospira-lineage labels omit: “Discard 30 days after first puncture,” “Protect from Light,” and “Refrigerate after opening.” Medibact does not supply that product and is not affiliated with its labeler; it is named here because it settles the question this section is about.
Two things follow, and they point in opposite directions. First, “bacteriostatic water is stored at room temperature” is a statement about a label, not about the substance — so the only safe instruction is to read the vial in front of you rather than any general rule, this page included. Second, that 30-day figure is longer than the compendial 28 days, which is exactly what §15.2 permits: the manufacturer may specify otherwise, and where it has, the printed period governs and the 28 days does not apply. A printed period is not automatically the more conservative one.
What the field does, and whose practice it is. Two conventions get compressed into one instruction online. The 28-day figure is compendial and applies to the container: USP <797> Section 15.2 says a punctured multiple-dose container “is not used for more than 28 days unless otherwise specified by the manufacturer on the labeling.” The 2 to 8°C figure is different — it is the in-use condition printed on the labels of reconstituted peptide products. GENOTROPIN directs that a reconstituted cartridge be stored at 2° to 8°C “between each use, for up to 28 days” — and those 5 mg and 12 mg presentations are the ones containing metacresol as a preservative. FORTEO directs storage at 2° to 8°C “at all times except when administering the product,” with the device discarded 28 days after first use.
| What is in the container | Stated temperature | Stated window | Source |
|---|---|---|---|
| Bacteriostatic water, unopened | 20–25 °C | Until the printed EXP date | FDA-approved labeling |
| Bacteriostatic water, after first puncture | 20–25 °C — label unchanged | 28 days from entry | USP <797> §15.2; CDC |
| Sterile water, single-dose, unpreserved | 20–25 °C | Up to 12 hours — only if entered in ISO Class 5 or cleaner air | USP <797> §15.1 |
| Somatropin cartridge, reconstituted, metacresol-preserved | 2–8 °C | Up to 28 days | GENOTROPIN labeling |
| Somatropin cartridge, reconstituted, preservative-free | 2–8 °C | Up to 24 hours after mixing | GENOTROPIN MINIQUICK labeling |
| Teriparatide multi-dose pen solution | 2–8 °C except while administering | 28 days after first use | FORTEO labeling |
| Compounded multi-dose aqueous preparation, non-preserved (topical or ophthalmic) | Room temp vs refrigerated | 24 hours vs 72 hours | USP <797> §14.5 |
The somatropin rows are the clearest illustration: same molecule, same 2 to 8°C, and the window differs by more than an order of magnitude — 28 days for the metacresol-preserved cartridges, 24 hours for the preservative-free MINIQUICK. The last row makes the point from the other side, within its own narrow scope: for a compounded non-preserved aqueous multi-dose preparation, where <797> names topical and ophthalmic solutions as the example, cold buys time — 24 hours at room temperature against 72 refrigerated. Preservative and temperature are two different levers. Bacteriostatic water pulls the first, and 28 days is already its cap.
How long does bacteriostatic water last?
Two clocks, and they are not the same clock. The printed expiry date covers the vial as supplied and sealed; it is the only date that exists until someone punctures the stopper. The 28-day after-entry window starts at first puncture, under USP <797> Section 15.2. Both then run at once, and CDC is explicit that the beyond-use date “should never exceed the manufacturer’s original expiration date.” The earlier governs.
The unpreserved product makes it concrete. Sterile Water for Injection, USP “contains no bacteriostat, antimicrobial agent or added buffer and is supplied only in single-dose containers.” Section 15.1 gives such a container up to 12 hours after initial entry — but only where it was entered in ISO Class 5 or cleaner air, and an opened single-dose ampule gets no storage period at all. Same water, same room temperature; the comparison of the two monographs sets out why.
Reading the date, lot and storage line on a real vial
The Hospira 30 mL vial panel is transcribed in the SPL as: 30 mL Multiple-dose / BACTERIOSTATIC WATER for Injection, USP / 0.9% benzyl alcohol added. NOT FOR USE IN NEONATES / LOT ##–###–AA EXP DMMMYYYY.
- EXP dates the sealed vial, not the contents in use. It stops being the operative date once the stopper is punctured; LOT is the field a recall or a documented storage excursion is keyed to.
- The preservative percentage tracks the presentation, not the quality: the 30 mL plastic vial is 0.9% (9 mg/mL), the 20 mL fill in a 30 mL glass vial 1.1% (11 mg/mL). Tray and vial NDCs differ — 0409-3977-03 holds 25 of 0409-3977-01.
- The tray adds “FOR DRUG DILUENT USE ONLY.” The neonate warning appears on both, and the labeling ties it to “the potential toxicity of benzyl alcohol in neonates.”
Handling mistakes this page exists to correct
- Storing the water the way the peptide is stored — and, more consequentially, the reverse swap: giving a reconstituted vial the water’s room-temperature line, which the somatropin and teriparatide labels above argue against directly.
- Starting the 28-day clock at delivery. It opens at first puncture; an unopened vial runs on its printed EXP alone.
- Reading label silence as a verdict. These labels say nothing about refrigeration in either direction. That is not a prohibition, and it is not permission.
Shipping and transport temperature
Transit sits explicitly inside the <659> definition — the excursions it permits are the ones experienced during shipping. How well that holds has been measured: Chowdhury and colleagues sent 36 packages carrying data-logging thermometers through simulated mail transit across winter and summer windows, and reported an average of 68.3% of transit time outside the 68 to 77°F range, with extremes of 5.1°F and 102.3°F (J Am Pharm Assoc 2023;63(3):847–852; PMID 36858884). The framing was non-specialty oral medications and no product actually travelled, so it is evidence about mail transit rather than about this vial: one arriving warm has probably had an ordinary journey.
What Medibact supplies
Medibact stocks USP-grade bacteriostatic water produced in an FDA-registered U.S. facility, sold for research use only. Medibact is not affiliated with Hospira, Pfizer, Eli Lilly or any other manufacturer named here; their labels are cited because they are the documents that answer the question, and nothing on this page describes how any of them should be used.
Where this sits in the rest of the reference
FAQ
Does bacteriostatic water need to be refrigerated?
No. The labeling gives one storage condition and it is not cold: “Store at 20 to 25°C (68 to 77°F). [See USP Controlled Room Temperature.]” None of the three DailyMed labels checked — 87d6e9dc, 99b0ef9b, ccadcf46 — mentions refrigeration.
Does bacteriostatic water need to be refrigerated after opening?
The label does not require it: none of the three labels checked changes the storage condition at first puncture. What changes is the clock, not the temperature — USP <797> §15.2 caps a punctured multiple-dose container at 28 days “unless otherwise specified by the manufacturer on the labeling.” The 2–8 °C instruction repeated online belongs to reconstituted peptide labels, not to the water.
Can you put bacteriostatic water in the fridge?
Nothing on the labeling prohibits it, and nothing on it endorses it either. The labeled 9 and 11 mg/mL benzyl alcohol concentrations are 26% and 31% of the solubility PubChem carries at 20 °C — but PubChem publishes no figure at refrigerator temperature, and the two it does publish (35,000 mg/L at 20 °C, 42,900 mg/L at 25 °C) fall as temperature falls, which is the wrong direction to reassure from. No stability study of this product at 2–8 °C was located. Refrigeration here is unstudied, not proven harmless.
Can bacteriostatic water be frozen?
Freezing takes it outside the only condition its labeling covers, and water expands about 9.1% by volume as it solidifies (USGS for water at 0 °C, NIST for ice), which stresses a sealed vial and its closure. Worth saying plainly: none of the three labels checked prints “do not freeze,” so that instruction is inference rather than label text — and at least one registered protocol, NCT01580696, froze a peptide suspended in bacteriostatic water on purpose.
How long does bacteriostatic water last after the first puncture?
Twenty-eight days from first entry. USP <797> §15.2 sets that for multiple-dose containers unless the manufacturer specifies otherwise, and CDC says an opened multi-dose vial “should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.” The unpreserved single-dose comparison is not a straight 12 hours: §15.1 allows up to 12 hours only where the container was entered in ISO Class 5 or cleaner air.
Does the printed expiry date still apply once the vial has been entered?
Yes, as a ceiling. CDC states the beyond-use date assigned at puncture “should never exceed the manufacturer's original expiration date.” Two dates then run at once — the printed EXP and 28 days from entry — and the earlier governs.
How do you tell if a vial should not be used?
The labeling states it directly: “Do not use unless the solution is clear and seal intact,” alongside the instruction that parenteral drug products “should be inspected visually for particulate matter and discoloration prior to administration.”
What does Medibact supply, and is this medical advice?
Medibact supplies USP-grade bacteriostatic water produced in an FDA-registered U.S. facility, for research use only. This page is label and standards education — not medical advice, not a dosing, route or frequency instruction. Medibact is not affiliated with any manufacturer named here.
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.