Peptide Reconstitution Calculator
Convert peptide vial size and bacteriostatic water volume into mg/mL concentration, mcg per insulin unit, units to draw per dose, doses per vial, and weeks of supply. Supports semaglutide, tirzepatide, BPC-157, TB-500, GHK-Cu, and retatrutide.
HEALTHThe Peptide Reconstitution Calculator turns a lyophilized peptide vial into a precise injection plan. Enter the peptide mass on the label, the volume of bacteriostatic water you added, your desired dose, and your insulin syringe size — it returns the concentration in mg/mL, mcg per insulin unit, units to draw, doses per vial, and weeks of supply. It is used by patients on physician-prescribed GLP-1 therapy (semaglutide, tirzepatide, retatrutide) and by researchers and biohackers working with BPC-157, TB-500, GHK-Cu, and other research peptides where accurate self-dosing on a U-100 insulin syringe is critical.
The math is straightforward. Concentration in mg/mL equals peptide milligrams divided by BAC water milliliters. For a standard U-100 insulin syringe (1 mL = 100 units, so 1 unit = 0.01 mL), micrograms per unit equals the mg/mL concentration multiplied by 10. Units to draw equals your dose in mcg divided by mcg per unit. Doses per vial equals total peptide in mcg divided by dose in mcg. Worked example: a 5 mg semaglutide vial reconstituted with 2 mL of bacteriostatic water yields 2.5 mg/mL, which is 25 mcg per insulin unit. For a 250 mcg weekly dose, you draw 10 units on a U-100 syringe, get 20 doses out of the vial, and the vial lasts roughly 20 weeks — though reconstituted peptides should be used within about 28 days refrigerated regardless of remaining doses.
Peptide Reconstitution Calculator
Calculate bacteriostatic water volume, peptide concentration, and the exact number of units to draw on a U-100 insulin syringe. Supports semaglutide, tirzepatide, retatrutide, BPC-157, TB-500, GHK-Cu and other lyophilized research peptides reconstituted with BAC water.
Reconstitution, Syringes, and Sterile Technique
Reconstitution means dissolving a lyophilized (freeze-dried) peptide powder back into liquid form so it can be drawn into a syringe. Bacteriostatic water - sterile water containing 0.9% benzyl alcohol as a preservative - is the standard diluent because the benzyl alcohol inhibits bacterial growth, extending the usable life of a multi-dose vial to approximately 28 days when stored refrigerated at 2-8 degrees C. Plain sterile water lacks this preservative and is single-use only. The concentration in mg/mL is simply peptide mass divided by BAC volume: a 5 mg vial reconstituted with 2 mL of BAC water yields 2.5 mg/mL.
U-100 insulin syringes are the standard tool for subcutaneous peptide injections. The "U-100" designation means 100 units per 1 mL, so each unit corresponds to 0.01 mL. To convert a concentration into mcg per unit: multiply mg/mL by 10. At 2.5 mg/mL that is 25 mcg per unit, so a 250 mcg semaglutide dose requires drawing 10 units. The 0.5 mL (50-unit) and 0.3 mL (30-unit) barrels show the same scale at higher resolution, which is helpful for low-volume draws under 20 units where reading accuracy matters most.
Safety basics: always swab the vial stopper and injection site with a fresh alcohol pad, never reuse needles, and dispose of sharps in an FDA-cleared sharps container. Swirl gently to dissolve the powder - never shake, as agitation can denature peptide chains. Reconstituted peptides must be refrigerated; do not freeze unless the manufacturer instructions specify it. Discard any vial that looks cloudy, discolored, or has visible particulates. This tool is an educational aid only. It does not replace the dosing instructions of a licensed prescriber, compounding pharmacist, or the FDA-approved label of an approved drug product.
Not medical advice. Peptide therapy requires evaluation, prescription, and monitoring by a licensed clinician. FDA-approved semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro, Zepbound) are prescription-only drugs in the United States. Research peptides and compounded products are not FDA-evaluated for safety, purity, or efficacy for the conditions consumers commonly use them for - clinical use carries real risk including impurity, dosing error, infection, and adverse events. Always confirm dosing with your prescriber before injecting.