Bacteriostatic water (bac water) for injection
Straight facts about bacteriostatic water for injection: its 0.9% benzyl alcohol preservative, the vial sizes, and the 28-day limit once opened.
- The benzyl alcohol
- 0.9%
- once the first needle goes in (CDC)
- 28-day period
- label the vial sizes
- either 20 or 30 mL
- store it at room temperature
- 68-77 F
Bacteriostatic water is sterile water meant for mixing powdered medications ahead of an injection; it carries 0.9% benzyl alcohol as a preservative. Thanks to its preservative, the same vial can supply more than 1 draw over several weeks. Should your medication call for a single-use liquid, you can look at plain sterile water.
What bacteriostatic water is used for
A dose can only be drawn into a syringe after liquid has been added to a medication that comes as a dry powder. According to the Hospira DailyMed label, this is a multiple-dose vial for diluting or dissolving drugs meant for injection. Aseptic technique lets you pull liquid more than 1 time from a vial; it means clean, germ-free handling at every needle entry.
Keep an unopened vial at a normal room temperature, from 68 to 77 F, which equals 20 to 25 C. The moment a needle goes through the rubber stopper, mark the date on the label. Under CDC injection safety rules, discard an opened multiple-dose vial within 28 days. This limit changes if the manufacturer gives a different shelf life. Do not use any vial after the expiration date shown by the manufacturer.
Bacteriostatic water for injection, USP: 0.9% benzyl alcohol
Each 1 mL of liquid includes 9 mg of benzyl alcohol, which is 0.9% by volume. Once your needle opens the rubber top, that preservative prevents bacterial growth inside the vial; without it, throw away leftover liquid after 1 draw.
The FDA label says it must not be used for any of the following:
- for newborns (neonates); nothing but sterile water without preservative gets used there
- as a replacement for fluids
- during spinal or epidural anesthesia
- given straight into a vein, because it can rupture red blood cells (hemolysis)
Bacteriostatic water for reconstitution of peptides, HGH and semaglutide
Reconstitution is the process of adding a measured amount of water to a dry drug powder to turn it into a liquid. Some prescription medicines use a liquid diluent when mixing powdered vials. Products include Omnitrope, a human growth hormone brand, and Novarel, an hCG brand. When you mix a vial with 0.9% benzyl alcohol water, the Novarel label gives it up to 30 days in the fridge.
Ozempic and Wegovy are FDA-approved semaglutide medicines, and each one comes in a prefilled pen. Peptide vials made by compounding and peptide vials meant for research aren't FDA-approved. Products such as BPC-157 and TB-500 are research items with no FDA label, so the vendor is the only source for mixing instructions. Not every medicine mixes well with benzyl alcohol; ask a pharmacist to check compatibility, and let your prescriber set each dose. Find the correct amount to add with the bacteriostatic water calculator.
Bacteriostatic water vs saline (bacteriostatic sodium chloride)
| Bacteriostatic water | Sterile water | Bacteriostatic saline | |
|---|---|---|---|
| What it is | Sterile water with 0.9% benzyl alcohol | Sterile water, nothing added | Salt water (sodium chloride) with a preservative |
| Use more than once | Yes, within 28 days of the first needle | No, use once | Only as its own label says |
| Mix a drug with it | If your drug label names it | If your drug label names it | Only if your drug label names it |
Use only the liquid named by your drug label or prescriber to mix your medication.
Bacteriostatic water vial sizes
| Vial | Where you find it | 2 mL mixes per vial |
|---|---|---|
| 10 mL | Peptide shops ($14.00 to $14.99 listed) | 5 mixes |
| 20 mL | Hospira label | 10 mixes |
| 30 mL | Hospira label, pharmacies and medical suppliers, with prices from $9.00 to $27.99 listed | 15 mixes |
Vials of 1 mL and 5 mL aren't among the Hospira label sizes. At pharmacies, the 30 mL bottle is the size you'll see most often. Mixing small vials, 1 person rarely finishes within the 28-day limit that starts at the first needle. Sellers: the buy bacteriostatic water page lists where to find it.
Questions people often ask
Is injectable bacteriostatic water the same as bac water?
Yes, that everyday short name is bac water, and it means Bacteriostatic Water for Injection, USP. They refer to precisely the same sterile water containing 0.9% benzyl alcohol.
Does bacstat water refer to the same product?
Yes, bacstat water is another shorthand name for that same multiple-dose water for injection. Make sure the bottle label lists the complete USP name and states 0.9% benzyl alcohol.
Does bacteriostatic saline count as a bacteriostatic solution?
It's a salt solution with a preservative, not plain water with a preservative. Use it only when either your drug label or your prescriber specifies it.
Can you make bacteriostatic water at home?
No, making it safely in a kitchen isn't possible. Commercial vials follow USP standards for sterile products; a home mix of boiled water and alcohol is neither sterile nor measured.
Does bacitracin water mean the same thing?
No, people often confuse these similar words. Bacitracin is an antibiotic medication; bac water, by contrast, holds nothing but sterile water along with 0.9% benzyl alcohol.