What it is
Sterile water for injection is very clean water. It is made to the standard needed for medicines given by needle. It is sterilised (made germ-free) and sealed. Nothing is added to it. There is no salt, no preservative and no buffer.
It is not a medicine on its own. The FDA-approved label gives it just one job. It is used to thin down or dissolve other injectable drugs. This is done by following the instructions from the maker of the other drug.
It has no preservative. So it is sold only in single-dose containers. The label says to throw away any water left over.
It has nothing dissolved in it. So it is far more watery than blood. If it went straight into a vein on its own, water would rush into red blood cells. The cells would swell and burst. This is called haemolysis. That is why the label says “not isotonic” and “hemolytic”. (Isotonic means balanced to match blood.)
Sterile Water for Injection, USP is Water for Injection that has been sterilised and packaged in single-dose glass or plastic containers, with no bacteriostat, antimicrobial agent or added buffer. With no solute it is strongly hypotonic relative to plasma. Infused intravenously on its own, it creates an osmotic gradient across the erythrocyte membrane; water enters the cells until they swell and lyse. The label accordingly states that intravenous administration without a solute may result in haemolysis, that the product must be made approximately isotonic before use, and that it should not be used for intravenous injection unless the osmolar concentration of additives gives an approximately isotonic admixture.
The label’s clinical pharmacology section describes water itself: about 70% of total body weight, an average adult daily requirement of two to three litres, and distribution governed largely by sodium concentration. The small volumes used as a pharmaceutical aid are described as unlikely to affect fluid balance except in neonates or very small infants. It has no pharmacological action of its own beyond serving as a solvent and vehicle.
Who made it and when
Sterile water for injection was not invented by one person. Its quality standard is set by the United States Pharmacopeia (the official US rule book for medicines). Several companies make and label it.
FDA records show Hospira’s product was approved on 27 October 1982. Hospira is now part of Pfizer. Hospira’s bacteriostatic water was approved on the same day. Other companies also have labels for sterile water for injection.
Some products have similar names but are not the same. They cannot be swapped for each other:
- Bacteriostatic water has a preservative. It is made to be used many times from one container.
- Sterile water for irrigation is made for rinsing. Its label clearly says it is not for injection.
- Sterile water for inhalation is made for breathing equipment.
Drugs@FDA lists NDA 018801 (Hospira) for Sterile Water for Injection, original approval 27 October 1982, with several container sizes currently marketed on prescription and a 1 mL presentation discontinued. The Hospira label on DailyMed was revised in March 2026. The companion bacteriostatic product, NDA 018802, carries the same approval date.
The related USP articles differ in ways that matter. Bacteriostatic Water for Injection contains 0.9% or 1.1% benzyl alcohol in a multiple-dose container and is contraindicated in neonates; its label directs that where water is needed to prepare medications for neonates, only preservative-free Sterile Water for Injection be used. Sterile Water for Irrigation (for example B. Braun, NDA 016734) is labelled “Not for injection” and warns that it is hypotonic and will cause haemolysis. Sterile Water for Inhalation is a separate USP article, prepared from Water for Injection that is sterilised and suitably packaged with no added antimicrobial agent, and named for inhalation use. The names are similar; the labelled routes are not.
What the data say
There are no studies testing how well sterile water for injection works. None would make sense. It is only used to mix other drugs. It does not treat any illness.
Instead, the safety facts come from the FDA label. The main danger is haemolysis (bursting of red blood cells). This can happen if the water goes into a vein without enough added to it to match blood.
The label also lists other problems. These can come from the water, the added drug or the injection itself:
- fever
- tenderness, an abscess (a pocket of pus), tissue damage or infection where the needle went in
- an inflamed vein or clots in the vein
Newborns and very small babies are a special case. For them, even the amount of fluid can affect their fluid and salt balance.
No efficacy trials exist for Sterile Water for Injection, because it is a vehicle with no therapeutic claim; the relevant evidence is the label’s safety content and basic physiology. The label’s adverse reactions section lists febrile response, local tenderness, abscess, tissue necrosis or infection at the injection site, and venous thrombosis or phlebitis extending from the injection site, attributed to the solution, added drugs or technique.
The principal product-specific hazard is haemolysis from intravenous administration of a solute-free, hypotonic fluid; the container statement “NOT ISOTONIC. HEMOLYTIC.” and the contraindication requiring an approximately isotonic admixture both address it. The label states that safety and effectiveness have been established in paediatric patients, with the caveat that in neonates or very small infants the fluid volume may affect fluid and electrolyte balance. Animal reproduction studies have not been conducted, and the label advises use in pregnancy only if clearly needed. Its overdosage section states that the product is to be used only as a diluent or solvent and is unlikely to cause fluid overload except possibly in neonates or very small infants.
Container integrity is the other product-specific risk: in a Class II recall initiated 2026-04-02 (D-0495-2026), B. Braun Medical Inc. withdrew two lots of its 3000 mL Pharmacy Bulk Package (NDC 0264-7385-60) for “Lack of Assurance of Sterility; potential for leakage from the diaphragm port once the foil is removed.”
Regulatory picture
Sterile water for injection is an FDA-approved prescription product. The approval covers one use only. It is for thinning or dissolving other injectable drugs, following those drugs’ own instructions. Mixing a drug into it does not make that drug approved.
Its label says it is single-dose. Each container is for one use. Anything left over is thrown away. This is the main difference from bacteriostatic water. Bacteriostatic water has a preservative, so it can be drawn from many times.
Sterile water for rinsing or for breathing equipment is a different product. It has a different label. The rinsing product clearly says it is not for injection. Pharmacy mixing (compounding) rules for raw drug ingredients do not apply here. This is because it is a finished, approved product.
Supply: some 1 mL vials have been on the FDA’s shortage list since 2021 because demand went up, while 10 mL vials were available when the list was last revised in October 2026. In April 2026 one maker recalled two batches of a large 3000 mL pharmacy container because the port could leak.
Sterile Water for Injection is marketed as a prescription pharmaceutical aid under NDA 018801 and other applications, with a single labelled indication: diluting or dissolving drugs for intravenous, intramuscular or subcutaneous injection according to the drug manufacturer’s instructions. The compounding field is recorded as not applicable because it is a finished approved product, not a bulk drug substance nominated for the 503A list.
FDA’s October 2018 guidance on package-type terms defines a single-dose container as a container of sterile medication for parenteral administration that is not required to meet antimicrobial effectiveness testing requirements and is designed for use in a single patient as a single injection or infusion, with appropriate discard statements on the label. The Hospira label follows that model with “Single-dose” and “Discard unused portion”. By contrast, a multiple-dose container must meet antimicrobial effectiveness testing, which is why the preserved bacteriostatic product exists as a separate article. Irrigation and inhalation grades are separate USP articles with their own labelling, and the irrigation label states that it is not for injection.
Supply: FDA’s drug shortage list carries Sterile Water Injection as “Currently in Shortage” (first posted 11/23/2021, latest revision 10/29/2026). The 1 mL presentations from Fresenius Kabi (NDC 63323-185-10) and Hikma (NDC 0641-6147-10) are listed as unavailable, with the reason “Demand increase for the drug” and next releases expected in October and November 2026 respectively; Nephron’s 1 mL (NDC 0487-6105-01) is listed as limited; Hospira’s 1 mL and 10 mL, Fresenius Kabi’s other 1 mL and 1000 mL, and Medefil’s 10 mL presentations are listed as available. A separate Sterile Water Irrigant entry (first posted 04/28/2023) is also “Currently in Shortage” after Otsuka ICU Medical’s presentations were listed under “Discontinuation of the manufacture of the drug”. The B. Braun 3000 mL recall (D-0495-2026) is recorded above.
