Printed on the vial label.
The total volume of diluent you put into the vial.
Syringe size (U-100)
Draw to
5 units
- Your dose
- 250 mcg = 0.25 mg
- Volume
- 0.05 mL
- Concentration
- 5 mg/mL
- Doses in this vial
- 40
| 5 units | 0.25 mg |
|---|---|
| 10 units | 0.5 mg |
| 20 units | 1 mg |
| 30 units | 1.5 mg |
| 50 units | 2.5 mg |
The starting values are examples. Replace them with what is on your vial label and prescription. This tool does the arithmetic only and does not recommend a dose.
How to use it
- Choose Powder vial if you add water yourself, or Pre-mixed liquid if the label already gives a concentration in mg/mL.
- Enter the amount in the vial and the water you add, or the concentration.
- Enter your dose and pick mcg or mg. Check the line that shows it in both.
- Pick the syringe you have. The result is the mark to draw to.
The formula
Three steps, shown here with a 10 mg vial, 2 mL of water and a 250 mcg dose:
- Concentration = amount ÷ water = 10 mg ÷ 2 mL = 5 mg/mL
- Volume = dose ÷ concentration = 0.25 mg ÷ 5 mg/mL = 0.05 mL
- Units = volume × 100 = 5 units
Mistakes this is built to catch
- mcg and mg swapped. The result always states the dose in both units.
- A draw too small to measure. You get a warning below the first mark, with the fix.
- A draw that does not fit. You get a warning when it is more than the syringe holds.
- A draw between marks. A 100-unit syringe is marked every 2 units, so odd numbers are a guess.
New to this? Read how to read an insulin syringe and the safety notes.
Common questions
How does a peptide calculator work?
It divides the amount in the vial by the water you add to get a concentration, divides your dose by that concentration to get a volume, then converts the volume to units on a U-100 insulin syringe (100 units per mL).
What is the difference between mcg and mg?
One milligram (mg) is 1,000 micrograms (mcg). Mixing them up changes the dose a thousandfold, so the calculator always shows your dose in both.
Does adding more water change the dose?
No. More water makes the solution weaker, so the same dose takes a larger draw. The amount of drug in the vial stays the same.
Are units the same as milligrams?
No. Units on an insulin syringe measure volume: 1 unit is 0.01 mL. How many milligrams that holds depends on the concentration of your vial.