BAC water is the solvent your peptides need. Short for bacteriostatic water, it is sterile USP water with 0.9% benzyl alcohol added, so a multi-dose vial stays usable for about 28 days once the first needle goes in. The hard part is buying it cleanly: chain pharmacies rarely sell it over the counter, Amazon pulled most listings, and online quality swings wildly. This page shows you where to buy tested BAC water, what it should cost, and why our pick is PureBac, the most transparent and tested option we found.
Quick Answer
BAC water is sterile water preserved with 0.9% benzyl alcohol, used to reconstitute lyophilized peptides like BPC-157, retatrutide, or tirzepatide. CVS, Walgreens, Walmart, and Costco almost never sell it to consumers off the shelf, and Amazon removed most listings, so the practical route is an online specialty supplier. Our tested pick is PureBac: a 10mL multi-dose vial at $14.99 with a 7-point batch test and a public Certificate of Analysis for every lot.
🔑 Key Takeaways
- PureBac is the tested pick. Every lot clears a 7-point batch test and ships with a public, per-lot Certificate of Analysis you can read without an account or a request form.
- Stores rarely sell it. CVS, Walgreens, Walmart, and Costco keep it pharmacy-gated and usually behind a prescription, and Amazon delisted most listings, so an online specialty supplier is the real route.
- Know what real BAC water looks like. USP sterile water plus 0.9% benzyl alcohol in a glass multi-dose vial with a metal crimp seal, not a soft plastic squeeze bottle.
- One 10mL vial goes a long way. It reconstitutes several peptide vials and stays good for about 28 days once opened, so most buyers overbuy.
- One honest limitation: PureBac is online only and costs slightly more per mL than a bulk pharmacy 30mL tray. The public paperwork and matched size still make it the smarter buy.
What bacteriostatic water (BAC water) is, in one minute
BAC water is sterile water plus a preservative. The preservative is benzyl alcohol at 0.9%, which is 9 mg per mL, the long-standing standard concentration that keeps the water bacteriostatic. That single ingredient is why you can stick a needle into the same vial day after day for about a month instead of throwing it out after one use.
Peptides ship as a dry, lyophilized powder. To dose one, you draw BAC water into a syringe and inject it slowly down the vial wall to dissolve the powder into a stable liquid. The benzyl alcohol holds back bacterial growth across the days or weeks you draw from that reconstituted peptide, which plain sterile water cannot do. If you want the full mixing walkthrough, our bacteriostatic water guide covers technique, ratios, and storage in detail.
That is the whole definition. Now the part most pages skip: where do you actually buy a clean vial, and which one is worth your money.
The best BAC water for peptides right now
PureBac is our top pick for 2026. The reason is simple and it is the same reason most online BAC water fails a careful buyer: paperwork. PureBac runs a 7-point test on every batch and posts a Certificate of Analysis for each lot number on its site. Most listings give you a clear vial and a price, and nothing else, no batch number, no published assay, no proof the benzyl alcohol is even at 0.9%.
The product itself is a 10mL multi-dose vial of PureBac bacteriostatic water at $14.99, sized to support roughly 28 days of repeated draws, which lines up with the open-vial window anyway. The table below shows how the main ways to buy BAC water stack up, with the column that actually separates them, tested with a public COA.
| Option | Vial size | Tested + public COA | Typical price | Best for |
|---|---|---|---|---|
| PureBac (recommended) | 10mL multi-dose, glass | Yes, 7-point batch test, per-lot COA posted online | $14.99, about $1.50/mL, bulk to $13.49/vial | Mixing peptides at home, one cycle per vial |
| Hospira / Pfizer pharma vials | 30mL multi-dose, glass | Strong factory QC, but no per-lot COA handed to retail buyers | $20 to $35, about $0.70 to $1.17/mL, Rx or wholesale gated | Clinics and large multi-month supply |
| Generic online vendors | 3mL to 30mL, varies | Sometimes claimed, rarely published | $8 to $50, wide quality swing | Budget buyers willing to vet a real COA |
| Amazon / marketplace | Varies, often unclear | No, listings restricted or removed | Varies, often mislabeled | Not recommended |
Brand-name pharmacy water from Hospira is excellent water. The friction is access and documentation, which we break down further below. For a buyer reconstituting peptides at home, a 10mL vial with a public COA beats a 30mL pharmacy tray you cannot easily get and cannot get paperwork for.
Inside PureBac's 7-point batch testing
Every PureBac lot clears seven separate checks. This is the centerpiece of why it earns the top spot, so here is what each test confirms and why it matters the moment you draw water into a syringe.
| Test | What it confirms | Why it matters for your peptides |
|---|---|---|
| 1. USP Water for Injection base | The water meets USP standards, free of organic and inorganic impurities | Your starting solvent is clean before the preservative is even added |
| 2. Identity | The preservative present is benzyl alcohol, not a substitute | You get the real bacteriostatic agent, not sterile water sold as BAC water |
| 3. Benzyl alcohol at 0.9% | The preservative sits at 9 mg/mL, the standard concentration | Enough to keep the vial sterile for repeat draws, not so much it stresses the peptide |
| 4. Heavy metals (ICP) | Lead, arsenic, mercury, and cadmium all fall below USP limits | No invisible contaminants riding along with every dose |
| 5. Endotoxins (LAL) | Non-pyrogenic, below the 0.25 EU/mL Water for Injection limit | Lowers the risk of an inflammatory reaction at the injection site |
| 6. Sterility | No aerobic or anaerobic bacteria or fungi, filled and sealed under aseptic conditions | A clear vial is not always a sterile vial, this confirms it is |
| 7. Batch-to-batch consistency | Every lot is checked to perform like the one before it | Your next order behaves the same as this one, with no surprises |
The transparency does not stop at testing. Every PureBac vial carries a unique lot number and a QR code, and the matching Certificate of Analysis lives on PureBac's site with no account and no request form to fill out. You scan the label, you read the assay for your exact batch. That is the paper trail almost no other seller gives you, and it is the difference between trusting a clear liquid and verifying it.
Where to buy BAC water
Most chain pharmacies do not stock it. Searches for "BAC water near me," "bac water CVS," "bac water Walgreens," and "bac water Walmart" almost always end the same way: it is not on a consumer shelf. Bacteriostatic water is an injectable drug product, so when a pharmacy carries it at all, it usually sits behind the counter and often needs a prescription. Costco is the same story. You may be able to ask a pharmacist to order a 30mL Hospira vial against a prescription, but you will not walk in and grab one off an aisle.
That leaves online specialty suppliers as the practical way to buy BAC water for peptides. This is where most home buyers actually shop, and it is also where quality is all over the map, from clean USP vials with published testing down to mystery bottles with no documentation at all. The fix is not to avoid online buying, it is to buy from a supplier that shows its work. PureBac sits at the transparent end because it posts a per-lot COA you can read before you order.
Why did Amazon stop selling BAC water?
Amazon quietly pulled most BAC water listings. If you have searched "why did Amazon stop selling bac water" or "bac water removed from Amazon," here is the plain version. Bacteriostatic water is an injectable drug product, and selling injectables to consumers runs into handling rules and, in much of the US, prescription requirements that a general marketplace is not set up to police. On top of that, marketplace listings had a recurring quality problem: some sellers shipped plain sterile water, or even 0.9% saline, labeled as bacteriostatic water. A marketplace also cannot guarantee how a vial was stored before it reached you.
So Amazon restricted and delisted the category rather than vouch for it. The takeaway for a buyer is not that BAC water is sketchy, it is that you should buy it from a supplier whose entire job is bacteriostatic water and who can prove what is in the vial. A published Certificate of Analysis does what an Amazon listing never could.
Hospira vs Pfizer vs third-party vials
Pfizer owns Hospira, so they are linked. Pfizer acquired Hospira in 2015, which means "Hospira bac water" and "Pfizer bac water" point to the same pharmaceutical line, most often the 30mL multi-dose glass vial you see referenced everywhere. Fresenius Kabi is another hospital-supply name in the same space. These are well-made, USP-grade vials built for clinical use.
The honest comparison is not about water quality, it is about access and proof. Brand pharmacy vials move through pharmacies and wholesalers, are frequently prescription-gated, and as a retail buyer you do not receive a per-lot Certificate of Analysis with your bottle. A clean third-party option like PureBac is made to the same USP spec, sized for home peptide use rather than a hospital cart, sold without a prescription wall, and shipped with the lot-level paperwork in public. So "Hospira bac water vs bac water" really comes down to whether you want a large clinical vial you have to chase down, or a right-sized vial with documentation you can verify in one click.
How much BAC water to buy, and what it costs
Most buyers need far less than they think. A single 10mL vial reconstitutes roughly five peptide vials at 2mL each, or about ten at 1mL each, and it only stays good for the 28-day open window once you puncture it. A 30mL pharmacy vial reconstitutes around fifteen 5mg peptide vials, a multi-month supply, but the clock starts at first puncture and every extra needle stick is one more chance to contaminate it. Buying bigger is not automatically buying smarter.
On price, BAC water runs about $10 to $20 for a typical single vial. PureBac is $14.99 for the 10mL, with volume pricing that drops the per-vial cost as you stock up: buy 3 at $14.54 each, 5 at $14.24 each, or 10 at $13.49 each, with free shipping over $150. Bulk BAC water makes sense if you run back-to-back cycles and will use it before it ages, otherwise buy fresh and skip the waste. Sealed and unopened, a vial is stable at room temperature, so you do not need to refrigerate your backups until you open them.
How to mix peptides with BAC water
Mixing takes about sixty seconds per vial. Draw your target volume of BAC water, insert the needle into the peptide vial, and let the water run down the inside glass rather than blasting it onto the powder. Swirl gently, never shake, and wait for a fully clear solution before you draw a dose.
The volume you add sets your dose math, which is where questions like "how much bac water for 10mg retatrutide" or "tirzepatide bac water calculator" come in. Rather than guess, run the numbers in our peptide reconstitution calculator, or browse the full peptide calculator suite. For drug-specific protocols, see our retatrutide dosing schedule and BPC-157 dosage guide, and if you are mixing for weight management, our roundup of peptides for weight loss ties the dosing back to goals.
Red flags when buying BAC water
A few warning signs save you money and trouble. Walk away from any vial that shows these, no matter how cheap it is.
Skip the listing if you see:
- No lot number and no accessible COA. If you cannot find the batch or read its testing, you are buying on faith.
- A soft plastic squeeze bottle. True BAC water comes in a glass multi-dose vial with a rubber stopper and a metal crimp seal. Plastic squeeze bottles are usually preservative-free sterile water, or mislabeled saline.
- A label that does not name the preservative. It should read something like "0.9% benzyl alcohol added as bacteriostatic preservative." Vague labels hide what is missing.
- A price under about $5 with zero documentation. Real USP water with testing costs money to make. Rock-bottom plus no paperwork is a tell.
- A marketplace seller with no manufacturer disclosure. No brand, no source, no returns policy is a gray-market gamble.
The single fastest check is the Certificate of Analysis. A seller who publishes a per-lot COA has already cleared most of this list for you, which is exactly why we keep coming back to it as the deciding factor.
The one honest limitation of PureBac
PureBac is online only, not pharmacy shelves. If you need a vial in your hand this afternoon, an online order cannot beat a local pharmacy that happens to stock one, and per mL the 10mL vial costs a little more than a bulk 30mL pharmacy tray bought at wholesale. Like every benzyl alcohol product, it also carries the standard caution that preserved water is not for use in newborns, the basis of the long-standing neonatal warning on these labels.
Here is why it still wins for a home buyer. You get a public, per-lot Certificate of Analysis with no account and no request form, a 7-point test behind every batch, and a 10mL size that matches a single cycle so you are not babysitting a giant vial past its open window. You get a glass multi-dose vial, a lot number, and a QR code instead of a faceless marketplace listing. Slightly higher per mL is a small premium for actually knowing what you are injecting, and most sellers cannot match a single line of that paper trail.
Frequently Asked Questions
References
- DailyMed (U.S. National Library of Medicine). Bacteriostatic Water for Injection, USP, label (Hospira, Inc.), including 0.9% benzyl alcohol, 28-day discard, and neonatal benzyl alcohol caution. dailymed.nlm.nih.gov.
- Pfizer Inc. Hospira injectables (Pfizer-owned), manufacturer of brand-name bacteriostatic water for injection. pfizer.com.
- Gershanik J, Boecler B, Ensley H, McCloskey S, George W. The gasping syndrome and benzyl alcohol poisoning. N Engl J Med. 1982;307(22):1384-1388. pubmed.ncbi.nlm.nih.gov.
- PubChem (U.S. National Library of Medicine). Benzyl Alcohol (CID 244), the antimicrobial preservative used in bacteriostatic water for injection. pubchem.ncbi.nlm.nih.gov.
- PureBac. The 7-Point Testing Protocol. purebac.com/testing.
- PureBac. Certificates of Analysis (per-lot COA library). purebac.com/coas.