Peptide reconstitution math, made legible.
A reference calculator for understanding how peptide vial concentration, bacteriostatic water volume, and a target dose translate into a measurable volume on a U-100 insulin syringe. Educational reference — not a prescription or instruction for human use.
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The math, explained
A peptide vial contains a fixed amount of lyophilized powder (e.g., 5 mg). When you add bacteriostatic water, the peptide dissolves into solution at a concentration determined by the ratio of peptide mass to water volume:
concentration (mcg/mL) = vial mass (mg) × 1000 ÷ water volume (mL)
To deliver a target dose, you need a volume of solution equal to the dose divided by the concentration:
volume (mL) = dose (mcg) ÷ concentration (mcg/mL)
A U-100 insulin syringe is graduated in units where 100 units = 1 mL. So the volume in mL translates to 100× that in insulin-syringe units.
insulin syringe units (U-100) = volume (mL) × 100
Frequently asked
What is bacteriostatic water?
Sterile water with 0.9% benzyl alcohol as a preservative, used to reconstitute injectable medications. It allows a vial to be opened and used multiple times without microbial growth, up to 28 days typically.
What is a U-100 insulin syringe?
An insulin syringe calibrated so that 100 'units' equal 1 mL. It's the most common syringe used for small-volume subcutaneous injections. The graduations make it easier to measure tenths of a mL than a typical 1 mL syringe.
Why is this presented as educational reference only?
Because this site does not publish dosing protocols for research-use-only peptides. Many peptides are legally available in the US only for laboratory research, not for human consumption. The math is the math; applying it to your own body is a clinical decision that belongs with a licensed clinician.
Does this calculator work for GLP-1 drugs like Wegovy or Zepbound?
FDA-approved GLP-1 drugs come in pre-filled pens or vials with manufacturer instructions; don't use this calculator for them. Use the manufacturer's prescribing information and your clinician's guidance.