Peptide reconstitution calculator
Calculate peptide concentration, injection volume, and exact syringe units for any peptide vial and target dose. Works universally for all research peptides.
Peptide reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide powder in a liquid solvent to create an injectable solution. Getting the reconstitution math right determines whether you receive the correct dose — errors compound at every step.
The universal standard solvent is bacteriostatic water: sterile water containing 0.9% benzyl alcohol. The benzyl alcohol acts as a preservative, inhibiting bacterial growth in the reconstituted solution and extending shelf life to approximately 28 days when refrigerated at 2-8°C. Sterile water without benzyl alcohol offers no protection against contamination and should not be used for multi-dose vials. Normal saline is appropriate for some clinical applications but is not the standard for peptide research.
Concentration is calculated by dividing the peptide mass (in micrograms) by the volume of bacteriostatic water added (in milliliters). Adding 2mL to a 5mg vial produces a concentration of 2500 mcg/mL. Adding 1mL produces 5000 mcg/mL. The choice of water volume affects the precision of smaller doses — higher concentration means smaller injection volumes that are harder to measure accurately on a syringe.
Most researchers use U-100 insulin syringes (100 units = 1mL). Each unit mark represents 0.01mL. For a concentration of 2500 mcg/mL, a 500 mcg dose requires 0.2mL — the 20-unit mark on a U-100 syringe. This calculator outputs the exact unit mark for your target dose given your reconstitution parameters.
For research use only. Always verify calculations before administration.
calc.concentration
2500 mcg/mL
2.500 mg/mL
calc.injectionVolume
0.100 mL
10 units (U-100 syringe)
calc.dosesPerVial
20
at 250 mcg per dose
Draw up to the 10 unit mark on a U-100 insulin syringe per dose. Always use bacteriostatic water (not sterile water) to extend reconstituted shelf life. Store at 2–8°C after reconstitution.
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Frequently asked questions
What is the difference between bacteriostatic water and sterile water for peptide reconstitution?+
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which inhibits bacterial and fungal growth. It is safe for multi-dose use and keeps reconstituted peptides stable for approximately 28 days refrigerated. Sterile water is preservative-free — it is sterile at opening but will allow microbial growth within 24 hours once punctured. For peptide research, bacteriostatic water is the universal standard.
How do I calculate peptide concentration after reconstitution?+
Concentration (mcg/mL) = peptide mass (mcg) ÷ water volume (mL). For a 5mg (5000 mcg) vial reconstituted with 2mL: 5000 ÷ 2 = 2500 mcg/mL. For a 10mg vial with 2mL: 10000 ÷ 2 = 5000 mcg/mL. The calculator handles this automatically — input your vial size and water volume to get the concentration instantly.
What size syringe should I use for peptide injections?+
U-100 insulin syringes are the standard. They come in 0.3mL (30 units), 0.5mL (50 units), and 1mL (100 units) barrel sizes. For small doses and concentrated solutions, a 0.3mL or 0.5mL syringe provides better graduation precision. For larger injection volumes, a 1mL syringe. Use the smallest barrel size that accommodates your injection volume — smaller barrels have finer markings between units.
How long does reconstituted peptide last in the refrigerator?+
Most peptides reconstituted in bacteriostatic water are stable for 28-42 days at 2-8°C (refrigerator temperature). This varies by peptide: more stable peptides like tirzepatide and retatrutide maintain potency longer; smaller, more fragile peptides like BPC-157 and sermorelin may degrade faster. Never freeze reconstituted peptides — ice crystals destroy the peptide structure.
Can I use the same vial of bacteriostatic water for multiple peptide vials?+
Yes — bacteriostatic water in a sealed multi-dose vial remains sterile for up to 28 days after first puncture when stored at 2-8°C. Use a clean syringe each time you draw from it. Do not add bacteriostatic water from a vial that has been punctured more than 10-15 times, as repeated needle punctures can compromise the stopper integrity.
Research background
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