How to use it
- Enter the amount of peptide printed on the vial, in mg.
- Enter how much bacteriostatic water you added (or will add), in mL.
- Enter your dose in mcg or mg and pick your syringe size.
- Read the units to draw. The syringe picture shows where the plunger stops.
Haven’t mixed yet? The How much water? tab works backwards: enter the units you’d like each dose to be and it tells you how much water to add.
The math behind it
Mixing spreads the powder evenly through the water, so the vial’s strength is mg in the vial ÷ mL of water. A U-100 insulin syringe holds 100 units in 1 mL, so the units to draw are dose in mg ÷ strength × 100.
| Vial | Strength | Dose | Draw | Doses per vial |
|---|---|---|---|---|
| 5 mg + 2 mL | 2.5 mg/mL | 250 mcg | 10 units (0.1 mL) | 20 |
| 10 mg + 2 mL | 5 mg/mL | 2 mg | 40 units (0.4 mL) | 5 |
| 30 mg + 3 mL | 10 mg/mL | 7.5 mg | 75 units (0.75 mL) | 4 |
Working backwards: for a 10 mg vial and 250 mcg doses to land on 10 units, add 4 mL of water.
Reading the syringe
Insulin syringes come in 0.3 mL (30 units), 0.5 mL (50 units) and 1 mL (100 units) sizes. The smaller the syringe, the finer its markings: a 0.3 mL syringe is often marked every 0.5 unit, larger ones every 1 unit or more. If your draw falls between marks, a little more or less water puts it on one, and the calculator flags draws that are hard to read.
New to this? Read Reconstituting a vial and reading syringe units, then storage: mixed vials without a label are usually kept in the fridge and used within 28 days.
Questions
- What is a "unit" on an insulin syringe?
- A U-100 insulin syringe is marked in units, where 100 units = 1 mL. A unit is a measure of volume on that syringe, not of how much peptide you get: that depends on how strong the mixed vial is.
- Are syringe units the same as IU?
- No. IU (international units) measure a drug’s activity, as on hGH or hCG vials. Syringe units only measure liquid volume. If your dose is in IU, divide the IU in the vial by the mL of water to get IU per mL, then work out the volume the same way.
- Does adding more water change my dose?
- No. More water makes the mix weaker, so the same dose takes more units (more liquid). The amount of peptide you get stays the same. More water makes small doses easier to measure; less water keeps the injection smaller.
- How do I convert mg and mcg?
- 1 mg = 1,000 mcg. A 250 mcg dose is 0.25 mg. The calculator takes the dose in either unit.
- How long does a mixed vial keep?
- Check the drug’s label first. Where there is no label or stability data, the common practice is to keep it in the fridge and use it within 28 days. The storage guide covers the details.
Example numbers show how the math works; they are not dose recommendations. Check every draw against your own vial and your prescriber’s instructions.