Bacteriostatic Water vs. Sterile Water: Which to Use

Bacteriostatic water (BAC water) contains 0.9% benzyl alcohol, which inhibits bacterial growth and allows multi-use vials to remain sterile for 28 days after first use. Sterile water contains no preservative and should only be used for single-dose preparations — it is not appropriate for multi-day peptide vials. For most research peptides (BPC-157, ipamorelin, CJC-1295, TB-500, MT-2, PT-141, GHK-Cu), BAC water is the correct choice. Exception: IGF-1 LR3 requires acetic acid for initial reconstitution (see the dedicated IGF-1 guide).

Reconstitution Technique

Step 1: Allow the lyophilized vial to reach room temperature before opening to prevent condensation. Step 2: Wipe the rubber stopper with an alcohol swab and allow to dry. Step 3: Draw the desired volume of BAC water into a sterile syringe. Step 4: Inject the water slowly down the inside wall of the vial — do not aim directly at the peptide powder. High-velocity liquid contact can shear peptide chains. Step 5: Gently swirl (do not shake) the vial until the powder is fully dissolved. The solution should be clear to slightly opalescent.

Calculating Working Concentrations

The formula: Concentration (mg/mL) = Vial amount (mg) ÷ Volume added (mL). Examples: 5 mg vial + 2 mL BAC water = 2.5 mg/mL. 10 mg vial + 2 mL = 5 mg/mL. To calculate volume per dose: Volume (mL) = Desired dose (mg) ÷ Concentration (mg/mL). For mcg-range doses (common with ipamorelin, GHK-Cu), multiply: a 2.5 mg/mL solution contains 2,500 mcg/mL. A 200 mcg dose requires 0.08 mL (80 units on an insulin syringe).

Common Mistakes That Degrade Activity

(1) Shaking vigorously — mechanical agitation denatures peptide structure. Always swirl gently. (2) Using hot water — heat accelerates hydrolysis and denaturation. Use room-temperature or refrigerated BAC water. (3) Leaving reconstituted peptide at room temperature — refrigerate immediately after reconstitution; most peptides are stable 2–4 weeks refrigerated but degrade rapidly at ambient temperatures. (4) Freeze-thawing reconstituted peptide — repeated freeze-thaw cycles cause aggregation. Aliquot into single-use portions before freezing if long-term storage is needed.

Storage After Reconstitution

Refrigerated (2–8°C): most reconstituted peptides are stable 2–4 weeks. Protect from light — amber vials or wrapping with foil extends this significantly. Frozen reconstituted peptide: technically possible for some peptides, but each freeze-thaw cycle causes some aggregation. If freezing is necessary, aliquot first. Lyophilized (unreconstituted): stable at room temperature for months, at -20°C for 2+ years. Reconstitute only what you plan to use within the stable window.