Peptide Science
Peptide Science

Reconstitution Fundamentals: BAC Water, Sterility, and Units

February 12, 2026• Peptide Science Editorial
guidereconstitutionsterilitymath

What “reconstitution” means

Reconstitution means dissolving a dry substance (often lyophilized powder) with a compatible sterile diluent to create a known concentration (amount per mL).

BAC water vs sterile water (conceptual)

  • Bacteriostatic water: sterile water with a preservative (commonly benzyl alcohol) intended for multiple withdrawals when appropriate.
  • Sterile water (preservative-free): generally intended for single-use contexts unless product labeling says otherwise.
  • Always verify compatibility and instructions in the product label/monograph for the specific substance.

Aseptic handling basics

  • Use a clean preparation area and clean hands.
  • Use new sterile needles/syringes for each access and each injection event.
  • Do not reuse or "top off" with previously used supplies.
  • Disinfect vial stoppers before access and avoid touching sterile needle tips.

Concentration math (core formula)

Concentration (mg/mL) = total peptide amount (mg) ÷ total reconstitution volume (mL)

Example: 10 mg reconstituted with 2 mL gives 5 mg/mL.

Converting mg and mcg

  • 1 mg = 1000 mcg
  • If concentration is 5 mg/mL, that is also 5000 mcg/mL.

Common pitfalls

  • Mixing up mg and mcg.
  • Forgetting final total mL after reconstitution.
  • Assuming all products can be handled identically.
  • Using unclear labels or undocumented concentrations.

Conservative quality-control checklist

  • Label vial with date/time of reconstitution and final concentration.
  • Track lot/batch and source documentation.
  • Discard if appearance changes unexpectedly (cloudiness/particles) unless product docs explicitly describe expected appearance.

Sources