Can I use normal water to reconstitute peptides?

No. Tap water contains minerals and microorganisms that can contaminate the peptide. You must use either bacteriostatic water (for multi-use vials) or sterile water for injection (single-use only).

How long does bacteriostatic water last once opened?

Bacteriostatic water remains sterile for up to 28 days after the vial is first punctured, when stored at room temperature and away from light. Sterile water for injection should be discarded immediately after a single use.

Diluents

Bacteriostatic Water: What It Is & Why It Matters

Q: What is bacteriostatic water?

Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth. It is used to reconstitute injectable medications and research peptides because it allows a vial to be punctured multiple times safely.

The diluent you choose determines how long your reconstituted peptide stays safe to use. BAC water, sterile water, and saline are not interchangeable.

TL;DR — BAC water contains 0.9% benzyl alcohol, which prevents bacterial growth. Use it for multi-draw vials. Sterile water is single-use only. Never use saline for peptides.

The Difference

BAC Water vs. Sterile Water vs. Saline

Diluent	Multi-Draw	Shelf Life (Open)
BAC Water 0.9% benzyl alcohol	Yes	28 days
Sterile Water No preservative	Single use	Discard immediately
Saline (0.9% NaCl) Sodium chloride	Avoid	Not recommended

Why not saline? Saline (sodium chloride solution) can affect the solubility and stability of some peptides. It is also not antimicrobial. Most peptide researchers use BAC water exclusively.

How It Works

What Benzyl Alcohol Does

The 0.9% benzyl alcohol in BAC water disrupts the cell membranes of bacteria, preventing them from colonizing the vial after it has been punctured. This makes it safe to draw from the same vial multiple times over 28 days.

Without it, every needle puncture introduces a small risk of microbial contamination. A 5 mg peptide vial reconstituted with BAC water can safely be drawn from 10+ times over a month-long protocol.

Note on benzyl alcohol sensitivity: Benzyl alcohol is generally well-tolerated, but individuals with known sensitivity should use sterile water (single-dose preparation only) or consult a healthcare provider.

Storage

After Reconstitution

Once a peptide vial is reconstituted with BAC water:

Refrigerate at 2–8°C — most peptides are stable 4–6 weeks

Protect from light — keep vials in their box or wrap in foil

Never freeze a reconstituted vial — ice crystal formation can degrade the peptide

FAQ

Common Questions

What is bacteriostatic water?

BAC water is sterile water for injection containing 0.9% benzyl alcohol. The benzyl alcohol acts as a preservative, preventing bacterial growth after the vial has been punctured. It is the standard diluent for research peptide reconstitution.

Can I use regular tap water or bottled water?

No. Tap water and bottled water contain minerals, microorganisms, and other contaminants that can degrade the peptide and introduce infection risk. Only use pharmaceutical-grade bacteriostatic water or sterile water for injection.

How long does bacteriostatic water last after opening?

BAC water remains antimicrobially effective for 28 days after the first puncture when stored at room temperature. After 28 days, discard and use a fresh vial.

Where can I buy bacteriostatic water?

BAC water is available at pharmacies, medical supply companies, and various online retailers. Look for "Bacteriostatic Water for Injection USP" to ensure pharmaceutical grade. ASCEND does not sell or endorse specific suppliers.

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