PeptideWise

Peptide Reconstitution Calculator

Lyophilized (freeze-dried) peptides must be reconstituted with bacteriostatic water before injection. Getting the measurements right is critical: too little water produces an overly concentrated solution that is difficult to dose accurately; too much water reduces concentration and increases injection volume.

Enter your vial amount, the volume of bacteriostatic water you plan to add, and your target dose to calculate the exact volume to draw for each injection.

Peptide amount in vial (mg)
Bacteriostatic water added (mL)
Desired dose per injection (mcg)

Results

Concentration
2500 mcg / mL
Volume per dose
0.100 mL

10.0 units on a U-100 insulin syringe

Doses per vial
20 doses

Syringe fill (U-100)

10.0 units
0255075100

How Reconstitution Works

Reconstitution is the process of dissolving a lyophilized peptide powder in a sterile solvent — typically bacteriostatic water — to create an injectable solution. Lyophilization (freeze-drying) preserves peptide stability during shipping and storage, but requires this preparation step before use.

The key relationship is: concentration = peptide amount divided by solvent volume. A 5 mg peptide dissolved in 2 mL of bacteriostatic water produces a 2,500 mcg/mL solution. To deliver a 250 mcg dose, you would draw 0.10 mL (10 units on a U-100 syringe).

Limitations

  • This calculator provides mathematical estimates based on the values you enter. It does not account for pipetting error, evaporation, or dead volume in the syringe.
  • Peptide concentration in the vial as-received may differ slightly from the labeled amount due to manufacturing tolerances (typically 5-10%).
  • This tool is for educational and research reference purposes only. It does not constitute medical advice.
  • Dosing guidance for specific peptides should come from a licensed healthcare provider, not a calculator.

Sources and References

  1. USP Injections and Implanted Drug Products. United States Pharmacopeia (USP).
  2. Pharmaceutical Compounding — Sterile Preparations (USP <797>). United States Pharmacopeia (USP).
  3. Reconstitution and Stability of Lyophilized Pharmaceuticals. Journal of Pharmaceutical Sciences.

Frequently Asked Questions

Why must I use bacteriostatic water (BAC water) instead of sterile water?
Bacteriostatic water contains 0.9% benzyl alcohol, a preservative that inhibits microbial growth. This allows the reconstituted peptide solution to be stored for multiple weeks when refrigerated. Sterile water for injection (SWFI) contains no preservative, so it is intended for single-use only. Using sterile water for a multi-dose vial significantly increases contamination risk.
How should I store a reconstituted peptide vial?
Store reconstituted peptide vials in a refrigerator at 2-8 degrees C (36-46 degrees F), away from light. Avoid freezing a reconstituted solution as ice crystals can damage the peptide structure. Most reconstituted peptides are stable for 4-8 weeks when refrigerated in bacteriostatic water, though stability varies by peptide. Lyophilized (dry) peptides can typically be stored at -20 degrees C for longer-term preservation before reconstitution.
What type of syringe should I use?
U-100 insulin syringes (100 units = 1 mL) are standard for subcutaneous peptide injections. They come in 0.3 mL, 0.5 mL, and 1 mL barrel sizes. Use the smallest barrel that accommodates your dose to maximize measurement accuracy. For example, if your dose is 0.10 mL (10 units), a 0.3 mL syringe offers better precision than a 1 mL syringe.
What is the correct mixing technique to avoid damaging the peptide?
Draw up the bacteriostatic water in a syringe and inject it slowly down the inner wall of the vial — do not shoot it directly onto the lyophilized powder cake. Gently roll the vial between your palms to mix; do not shake or vortex. Shaking can cause peptide aggregation and denaturation, reducing potency. The solution should become clear and free of visible particles.
Why does the calculator show "doses per vial" as a decimal number?
The doses-per-vial figure is a mathematical result based on your inputs. A non-integer value (e.g., 20.4 doses) means your last draw will be a partial dose. In practice, you will get the floor of this number as full doses. Any remaining volume in the vial may not be sufficient for a complete dose at your chosen amount.
Is it safe to reconstitute peptides at home?
Reconstitution requires aseptic technique: using sterile supplies, working in a clean environment, swabbing vial septa with alcohol wipes, and never touching needle tips. Even with proper technique, home reconstitution carries contamination risks not present in a pharmaceutical or clinical compounding setting. Consult a licensed healthcare provider before handling injectable compounds.