OptiPin
How much did I actually take?
Work backwards from the units you drew to the milligrams you actually injected. For when the number on the syringe and the number in your head do not match.
Units to milligrams at your concentration
Everything that follows assumes the concentration shown above. Change the vial or the water and every row moves, which is the whole reason this mistake is so common.
| Units drawn | Volume | Dose |
|---|
Log the dose as you draw it
OptiPin stores the concentration of every open vial, so the units you draw are converted to milligrams and logged the moment you take them. No arithmetic at 6am, and no reconstructing it later.
Download on the App StoreHow to use this calculator
Why this goes wrong so often
Units are not a dose. A unit is a volume, one hundredth of a millilitre, and nothing more. The same 20 units is 1 mg from one vial and 4 mg from another. Any dose you remember as "twenty units" is only meaningful alongside the concentration it came from.
The trigger is almost always a new vial. People carry the unit count across from the old vial out of habit. If the new one is twice as concentrated, that habit is a double dose. The vial transition calculator exists specifically for that switch.
Insulin syringes are labelled for insulin. The scale assumes U-100 insulin, so the printed numbers mean nothing for peptides beyond the volume they represent.
Common questions
How do I work out how much I injected?
Multiply the volume you drew by the concentration in the vial. On a U-100 insulin syringe, units divided by 100 gives you millilitres, so 22 units is 0.22 mL, and at 5 mg/mL that is 1.1 mg.
How many mg is 20 units?
There is no single answer. Twenty units is always 0.2 mL, but the dose depends entirely on concentration: 0.2 mg at 1 mg/mL, 1 mg at 5 mg/mL, 40 mg at 200 mg/mL.
I drew too much. What now?
This tool tells you the size of the error, not the clinical significance of it. For a meaningful overdose, or if you feel unwell, contact a clinician or your local poison control line rather than waiting it out.
Does the water I added change the dose?
It changes the units, not the milligrams available in the vial. Ten milligrams in 1 mL and ten milligrams in 4 mL contain the same drug; the second is spread thinner, so the same dose takes four times as many units.
Does this work for testosterone as well as peptides?
Yes. Switch to the concentration tab and enter the mg/mL printed on the vial, commonly 200 mg/mL for cypionate. The arithmetic is identical.
Related tools
Peptide dose calculator
The forward direction: dose to units, for 200+ compounds.
Vial transition calculator
New vial, different concentration, same dose. The usual cause of this mistake.
Half-life calculator
How long an extra dose stays in your system.
Split dose calculator
Spreading a weekly dose across more injections.