Arithmetic on the numbers you enter. Check the result against your pharmacy label and ask your prescriber. Reko does not suggest doses, and this is not medical advice.
How it works
Units = dose ÷ concentration × 100. Use the concentration printed on your vial or pharmacy label.
Keep the record
Reko logs each dose against the vial or pen it came from, counts down what is left, and warns when a draw falls between your syringe's markings.
Key takeaways
- Units = dose ÷ concentration × 100.
- Concentration written as 'mg in 0.5 mL' must be turned into mg per mL first.
- Compounded and manufactured vials have different strengths. Never assume.
- Read the concentration off your own vial every time.
What this tool does
This tool converts a dose in milligrams, plus the strength of your vial, into the number of units to draw on a U-100 syringe. It is a converter, not a dosing tool. The dose is yours and your prescriber's.
How the arithmetic works
- Concentration (mg/mL) = mg in vial ÷ mL in vial. For a vial labelled 5 mg in 0.5 mL, that is 5 ÷ 0.5 = 10 mg/mL.
- Volume (mL) = dose (mg) ÷ concentration.
- Units = volume × 100.
A worked example
Example. These numbers are made up to show the steps. They are not a label value and not a suggestion.
A made-up vial at 10 mg/mL, and a wanted dose of 2 mg.
- 2 ÷ 10 = 0.2 mL.
- 0.2 × 100 = 20 units.
The same dose from a vial at 5 mg/mL is 40 units. Change vial, change units, and the dose is the same.
What to check against your label
- The concentration printed on the vial, in mg/mL or as an amount in a volume.
- The dose steps in the label for semaglutide. See the Ozempic and Wegovy dose charts.
- The syringe scale (U-100 assumed).
- The expiry and the storage rules once opened.
Frequently asked questions
Why do two vials give different units for the same dose?
Because the strength differs. Units track volume, not dose.
Can I use any syringe?
The sums assume U-100. Other scales change the answer.
What if the answer has decimals?
A syringe reads at its markings. A draw between markings cannot be measured, so ask whoever supplied the vial about a different mix or syringe.
Is this a prescription?
No.
How Reko does this in the app
In Reko you log the dose in milligrams, which is what matters, and attach the vial. Reko works out what is left in the vial from the doses you record. See the vial tracker.
Reko records what you and your prescriber decide. It never suggests a dose, and this page is not medical advice.