Peptide reconstitution calculator

Bacteriostatic water is sterile water with about 0.9 percent benzyl alcohol added as a preservative. It’s the diluent most commonly used to reconstitute lyophilized peptides because the preservative inhibits microbial growth long enough to use the vial across multiple injections.

The 28-day rule is the manufacturer-stated stability window once the preservative has been introduced — after 28 days, the bacteriostatic protection is no longer assumed to hold. Joust tracks this per-vial as the BUD (beyond-use date) and warns you before it elapses.

Insulin syringes are calibrated in units. U-100 means 100 units per millilitre; U-40 means 40 units per millilitre. The same volume of fluid reads a different unit number depending on which syringe you’re looking at, so the choice matters when you’re converting a target dose into a number to draw to.

U-100 (red cap, in most regions) is the more common choice for peptide work and matches what most pharmacies stock. U-40 (yellow cap) is more common in veterinary contexts and in regions where U-40 insulins are still used. Pick whichever one matches the physical syringe in front of you.

Total mg in the vial is fixed by the manufacturer — adding more or less bacteriostatic water doesn’t change how much active is in the vial, only how that mass is distributed across volume. Reconstituting a 10 mg vial with 1 mL gives 10 mg/mL; the same vial reconstituted with 2 mL gives 5 mg/mL.

More water means a lower concentration, which means each dose takes up a larger volume — and a larger number of units on the syringe. Doses-per-vial stays the same regardless: a 10 mg vial at 1 mg per injection yields ten injections either way. People choose more water when they want easier-to-read draw amounts and less when they want fewer units per injection.