Guides
Short explanations of the units and arithmetic behind the calculators. They cover how to read the numbers and how to check them. They do not cover what dose to use; that comes from your prescriber.
- How to read a U-100 insulin syringeUnits versus mL, the three barrel sizes, and what each tick mark is worth.
- Units vs mg vs mLWhy "how many units is 1 mg" depends on the vial, and the one number that settles it.
- mcg vs mgThe conversion, a table, and how to spot a result that is 1,000 times off.
- Bacteriostatic water vs sterile waterWhat each one is according to its label, and why the choice does not change the arithmetic.
- How water volume changes the mathsOne vial at 1, 2, 3 and 5 mL: what changes, what stays the same, and what each tick is worth.
- U-100 vs U-40 syringesA unit on a U-40 barrel is 2.5 times the volume of a unit on a U-100. Table and identification.
- IU vs mgAn IU measures activity, not weight, so the factor is different for every substance.
- How to double-check a calculator result by handThree independent pen-and-paper checks, and a table of the errors each one catches.
- How to read a vial labelWhere to find the amount, the concentration on pre-mixed vials, the lot number and the dates.
- Glossary of reconstitution termsPlain definitions of lyophilized, diluent, concentration, U-100, IU, beyond-use date and the other words on a vial label.
The arithmetic in three lines
concentration (mg/mL) = amount in vial (mg) ÷ water added (mL)
volume to draw (mL) = dose (mg) ÷ concentration (mg/mL)
syringe units = volume (mL) × 100 (U-100 syringe: 100 units = 1 mL)
Each guide explains one part of this. To run the numbers, use the calculator, a page under calculators by peptide, the conversion tables or the single-purpose tools. The how it works page has the short version.