Every result comes from three steps you can check by hand. This is the core of peptide reconstitution math:
- Concentration
mcg/mL = peptide mg × 1,000 ÷ water mL
- Volume to draw
mL = desired amount mcg ÷ concentration
- Syringe units
units = mL × 100 (U-100 syringe)
Worked example. A 5 mg vial with 2 mL of bacteriostatic water is 5,000 ÷ 2 = 2,500 mcg/mL, or 25 mcg per unit. 250 mcg ÷ 2,500 = 0.10 mL = 10 units. The vial holds 5,000 ÷ 250 = 20 draws.
| Vial | Water | Concentration | Amount | Units |
| 5 mg | 2 mL | 2,500 mcg/mL | 250 mcg | 10 |
| 10 mg | 2 mL | 5,000 mcg/mL | 1 mg | 20 |
| 10 mg | 1 mL | 10,000 mcg/mL | 500 mcg | 5 |
| 15 mg | 3 mL | 5,000 mcg/mL | 2.5 mg | 50 |
| 30 mg | 3 mL | 10,000 mcg/mL | 2 mg | 20 |
Choosing a water volume
Water doesn't change how much peptide is in the vial, only its concentration. More water gives larger, easier-to-read draws for small amounts; less water gives smaller draws for large amounts, where small measuring errors matter more. A practical range is 5–50 units per draw. The calculator suggests volumes that land on whole units, and Reverse mode finds the exact volume for any mark: water mL = peptide mcg × (units ÷ 100) ÷ amount mcg.
Understanding U-100 syringe units
U-100 insulin syringes are graduated so 100 units = 1 mL, so 1 unit = 0.01 mL on 0.3 mL, 0.5 mL and 1 mL barrels alike. Smaller barrels have finer, more widely spaced markings, which makes a 0.3 mL syringe easier to read for draws under 30 units. International Units (IU) are different: they measure biological activity and can't be converted from mg with a universal formula.
Storage basics
Lyophilized material is typically stored cool, dark and dry. Reconstituted material is commonly kept refrigerated at 2–8 °C, protected from light, and used within about four weeks. Label every vial with the compound, concentration and date — the vial-label button does this — and follow the product's documentation.