Bacteriostatic Water: What It Is and How It Relates to the Wolverine Stack

Bacteriostatic water is sterile water for injection with 0.9% benzyl alcohol added as a preservative, used to dissolve or dilute injectable medicines and supplied in multiple-dose vials. Sterile water for injection, by contrast, has no preservative and is single-dose. If you are prescribed the Wolverine stack through telos rx, it arrives ready to inject, so you never need bac water at all.

Bacteriostatic water comes up constantly in peptide conversations, usually as a shopping-list item. This guide explains what it is, how it differs from other sterile liquids, the safety points those lists skip, and why a prescription that arrives ready to inject takes it off the list entirely.

We are not going to walk through mixing steps here. Our peptide reconstitution explainer describes what research-vial buyers have to do and why it is error-prone, and the BPC-157 dosing, reconstitution and storage guide covers what the literature documents for BPC-157. If you have a prescription, your own pharmacy label always comes first.

Also searched as: bac water, bacteriostatic water for peptides, wolverine stack peptide, bpc 157 tb 500, bpc157 and tb500.

What is bacteriostatic water?

According to the FDA-listed product label on DailyMed, Bacteriostatic Water for Injection, USP is a sterile, nonpyrogenic preparation of water for injection containing 0.9% (9 mg per mL) benzyl alcohol, added as a bacteriostatic preservative (DailyMed label). The vial is marked Rx only, "for drug diluent use only" and multiple-dose.

Three words in that description matter:

• Sterile: it is free of living microorganisms when sealed.
• Nonpyrogenic: it is free of fever-causing contaminants.
• Bacteriostatic: the benzyl alcohol inhibits the growth of bacteria that might get in after the stopper is punctured. It slows growth; it does not sterilise the vial or make poor technique safe.

Bac water is not a medicine in its own right. It is a carrier a drug is dissolved in before injection.

Why bacteriostatic water is used for lyophilized peptides

Many peptides are commonly manufactured as a lyophilized (freeze-dried) powder. Peptides are generally more stable dry than in solution, so a powder can be stored and shipped more easily. Before injection, that powder has to be dissolved in a suitable sterile liquid, a step called reconstitution.

Where a single vial will be drawn from more than once, a preserved diluent such as bacteriostatic water is commonly chosen, because each needle puncture is a chance for bacteria to enter. Where a vial is used once and the remainder discarded, a preservative-free diluent may be used instead. Which one is right depends on the specific medication, and that decision belongs to the pharmacy and prescriber. With a telos rx prescription the pharmacy has already done this step, so your medication arrives ready to inject.

Bacteriostatic water vs sterile water vs saline

These liquids look identical in a vial. They are not interchangeable.

The DailyMed label for sterile water for injection describes it as containing no bacteriostat, antimicrobial agent or added buffer, supplied only in single-dose containers (DailyMed label). That is the core difference from bacteriostatic water: once a single-dose container is opened, nothing in it holds back bacterial growth.

Bacteriostatic water safety notes

Bacteriostatic water is routine in pharmacy practice, but the label carries real warnings.

Benzyl alcohol and newborns

The bacteriostatic water label states that, due to potential toxicity of benzyl alcohol in neonates, solutions containing it must not be used in that population. The warning traces back to cases in premature infants described in the early 1980s, including a 1982 report on the "gasping syndrome" and benzyl alcohol poisoning (Gershanik et al., 1982, PMID 7133084).

Single-use vs multi-dose

A multi-dose vial is not an open-ended supply. CDC injection-safety guidance says that once a multi-dose vial is opened, it should be dated and discarded within 28 days unless the manufacturer states another date, and never past the original expiry (CDC injection safety). A compounded medication also has its own beyond-use date on the pharmacy label, and that is the date that applies to it.

Never improvise diluents

Tap water, bottled water, distilled water from a shop, contact-lens solution or a different vial "that looks the same" are not substitutes. They are not made for injection and can introduce contaminants. This is one of the most common ways people mixing research vials at home get into trouble. A telos rx prescription avoids the problem because it arrives ready to inject, with no diluent involved. If anything about your medication is unclear, message your care team.

Allergies and other cautions

Some people react to benzyl alcohol. Tell your provider about allergies and any reaction to a previous injection. Do not use a vial if the liquid is cloudy, discoloured or the seal is broken; the label itself says to use it only if the solution is clear and the seal intact.

A note on bacteriostatic water maths

Searches for bacteriostatic water often come with a calculator attached. The arithmetic is simple: concentration equals the amount of drug divided by the volume of liquid.

Illustration only, not a dosing recommendation: a hypothetical vial holding 10 mg of a substance, dissolved in 2 mL of liquid, would contain 5 mg per mL.

That is exactly why a generic chart is risky for anyone mixing a research vial. The amount in a vial, the volume of liquid and the dose all have to line up, and a single slip changes the dose. With a telos rx prescription there is no maths to do: the pharmacy prepares it at the dose your provider prescribed, and it arrives ready to inject.

Bac water and the Wolverine stack (BPC 157 TB 500)

The Wolverine stack is a nickname for BPC-157 and TB-500 used together. The name refers to a fictional character known for fast healing, and it overpromises. For a full introduction, see what the Wolverine peptide stack is.

BPC-157 is a synthetic 15-amino-acid peptide derived from a sequence in a protein found in human gastric juice, studied mainly in animals for tendon, ligament, muscle and gut-lining repair. TB-500 is a synthetic fragment based on the actin-binding region of thymosin beta-4, studied for cell migration and wound repair. Human evidence for both is very limited. BPC-157 is not FDA-approved, and TB-500 is not FDA-approved either.

Grey-market "research use only" peptide vials are often sold alongside bac water as a do-it-yourself kit. Those vials are not made for human use, and their quality is unverified: they can be contaminated, mis-dosed or contain the wrong compound. Clean bacteriostatic water does not fix a questionable vial. Our guide to compounded vs unregulated BPC-157 explains the difference.

On regulation: in July 2026 the FDA's Pharmacy Compounding Advisory Committee voted to recommend adding BPC-157 and TB-500 to the compounding bulks list, a non-binding step. On October 28, 2026, HHS announced an interim enforcement discretion policy naming six peptides, including BPC-157 and TB-500, while FDA completes rulemaking; it is temporary, conditional and not FDA approval. Details are in TB-500 regulatory status after the PCAC vote.

For athletes: both peptides are on the WADA Prohibited List at all times (S0, non-approved substances; TB-500 is also covered by S2). Tested athletes should not use them.

How the Wolverine stack works with telos rx

telos rx offers the BPC-157 + TB-500 stack as two separate single-ingredient compounded subcutaneous vials under one provider-set plan. telos rx does not offer TB-500 on its own; if BPC-157 alone fits better, there is also BPC-157 injection.

1. Online intake. You answer health questions online, with no scheduled appointment.
2. Asynchronous provider review. A US-licensed provider reviews your answers. A prescription is required, and every prescription is subject to medical approval by a licensed provider. Approval is not guaranteed.
3. Licensed pharmacy. A licensed US pharmacy compounds your medication and dispenses it ready to inject at the dose your provider prescribed. There is nothing to mix and no dose to calculate, and the label and care team explain how to use and store it.
4. Ongoing support. Secure messaging with the care team, and plans can be paused or cancelled.

Side effects reported or theorised for BPC-157 and TB-500 include injection-site reactions, headache, nausea, dizziness, fatigue and flushing, and long-term human safety is not established. People with cancer or a cancer history are commonly advised to avoid them, and they are not for pregnancy or breastfeeding. Your provider weighs all of that. For pricing, see our sibling guide on what the Wolverine stack costs, and for how it compares with four-peptide blends, Wolverine stack vs KLOW stack. You can also go straight to the Wolverine stack page.

Bacteriostatic water: frequently asked questions

What is bacteriostatic water?

Bacteriostatic water is sterile water for injection that contains 0.9% benzyl alcohol (9 mg per mL) as a preservative. It is a prescription diluent used to dissolve or dilute medications for injection, and it is supplied in multiple-dose vials.

Is bac water the same as sterile water?

No. Bac water contains benzyl alcohol, which inhibits bacterial growth after the vial is opened. Sterile water for injection has no preservative and comes in single-dose containers, so any unused portion is discarded.

Why is bacteriostatic water used with peptides like BPC-157 and TB-500?

Many peptides are made as a freeze-dried powder because that form is more stable. A liquid is needed to dissolve the powder, and where a vial will be drawn from more than once, a preserved diluent such as bacteriostatic water is commonly used. A telos rx prescription arrives ready to inject, so no diluent is needed.

Is bacteriostatic water safe?

It is widely used as a diluent, but it is not for everyone. Benzyl alcohol has been linked to serious toxicity in newborns, so the label says not for use in neonates. Tell your provider about any allergies. telos rx prescriptions arrive ready to inject, so patients do not handle any diluent.

How much bac water do you add to a Wolverine stack peptide?

With a telos rx prescription, none. It arrives ready to inject at the dose your provider prescribed, so there is nothing to add and nothing to work out. For research vials the volume varies by product and is not something to take from a chart online. Any maths in this article is illustration only, not a dosing recommendation.

Does telos rx offer TB-500 on its own?

No. telos rx does not offer TB-500 on its own. It offers the BPC-157 + TB-500 stack, BPC-157 injection and BPC-157 capsules, each subject to medical approval by a licensed provider.

Is the BPC 157 TB 500 stack FDA-approved?

No. BPC-157 is not FDA-approved, and TB-500 is not FDA-approved either. telos rx prescribes the stack as two separate compounded vials from a licensed US pharmacy after an online review by a US-licensed provider. Approval is not guaranteed.

This article is for general education and is not medical advice. Nothing here is an instruction to prepare or inject any medication. BPC-157 is not FDA-approved, TB-500 is not FDA-approved, and compounded medications are not FDA-approved. All prescriptions are subject to medical approval by a licensed provider; approval is not guaranteed. Always follow your pharmacy label and care team. telos rx is an online-first, asynchronous telehealth service and is LegitScript-certified. Medications are compounded by a licensed US pharmacy.