Peptide Calculator

Reconstitution means adding a set amount of sterile liquid to a vial of powdered drug so it can be drawn into a syringe. The math has three steps: find the strength of the mixed liquid, the volume that holds your dose, and that volume on your syringe.

What the Peptide Calculator Measures

It measures volume, not dose. You bring the numbers your prescriber or pharmacist has already set: the peptide in the vial, the liquid added and the dose. The calculator turns them into a syringe reading. It does not suggest or check doses, schedules or products.

The Formula

Strength (mg/mL) = peptide in the vial (mg) / liquid added (mL)

Volume to draw (mL) = dose (mg) / strength (mg/mL)

Units on a U-100 syringe = volume to draw (mL) x 100

Full doses per vial = liquid added (mL) / volume drawn per dose (mL), rounded down

A dose in mcg is divided by 1,000 first, since 1 mg = 1,000 mcg. The "x 100" step works because U-100 means 100 units in each mL, so each unit on a U-100 syringe is 0.01 mL¹.

How This Calculator Computes Your Result

Enter the peptide in the vial (mg), the liquid added (mL) and your dose (mcg or mg). For a vial that came already mixed, enter the total mg and total mL from its label. Then pick your syringe (a 0.3, 0.5 or 1 mL U-100 insulin syringe, or a 1 or 3 mL syringe marked in mL) and the smallest mark printed on it.

The volume is rounded to the nearest mark (an exact half rounds down), and the result shows the dose that mark really holds. Numbers use a leading zero (0.5, not .5) and no trailing zeros (1, not 1.0), as ISMP advises⁵. You get a warning instead of a reading if the dose is more than the whole vial (often an mcg and mg mix-up), more than the syringe holds, or too small to measure.

What Your Result Means

A gap of more than 5% between your dose and the nearest mark is flagged. On a syringe marked every 2 units, for example, a 3-unit volume can only be read as 2 units, a third less.

This table shows how much peptide each 1-unit mark holds (10 x mg in the vial / mL added). These numbers show the math only, not doses for any product.

Worked example: 10 mg mixed in 2 mL gives 5 mg/mL. A 1 mg dose is 0.2 mL, which is the 20-unit mark on a U-100 syringe, and the vial holds 10 full doses.

Units, mL and mg: Where Measuring Mistakes Happen

A unit mark is a volume, not an amount of drug, so "10 units" from two vials of different strength are two different doses.

In 2024, FDA warned of overdoses from compounded semaglutide in vials, linked to confusion between mL, mg and "units"². Some patients told to draw 5 units (0.05 mL) with a 1 mL U-100 syringe drew 50 units, and patients in these reports took 5 to 20 times more than the intended dose². Some needed hospital care². ISMP reported the same mix-up, 0.5 mL (50 units) injected instead of 0.05 mL (5 units), and a hospital seeing more emergency visits from overdoses measured with insulin syringes³.

ISMP lists other common slips:

• Reading "U-100" as 100 units per vial instead of per mL, or mistaking units for mL⁴.

• Writing "U" for units, which can be read as a 0 or a 4 and cause a 10-fold or larger overdose⁵.

• Writing "µg" for micrograms, which can be read as mg. "mcg" is safer⁵.

• A missing leading zero (.5 mg read as 5 mg) or a trailing zero (1.0 mg read as 10 mg)⁵.

Peptide Safety and Mixing Liquids

Compounded drugs are not FDA-approved, so FDA does not check their safety, effectiveness or quality before they are sold⁶. As of April 2026, FDA's page on compounding substances that may present significant safety risks lists BPC-157 among nominations that were withdrawn. It was previously in the safety-risk group, and the page still says compounded BPC-157 may cause immune reactions and impurity problems, and that FDA lacks enough information to know whether it would harm people⁷.

Bacteriostatic water is sterile water with benzyl alcohol as a preservative, 0.9% (9 mg per mL) in a common version⁸. Its label says it is only for diluting or dissolving drugs for injection, and that newborns should get only preservative-free sterile water because benzyl alcohol has been linked to toxicity in them⁸. It also warns that some drugs may not be compatible, and that the volume depends on the drug maker's directions⁸. So the liquid and its amount should come from your pharmacist or the product's instructions.