Three small conversions cause almost all the confusion — and almost all the dangerous mistakes — in peptide and injectable math: mg to mcg, concentration (mg per mL), and volume to units on a U-100 syringe. Get these three straight and the arithmetic stops being scary. This is a plain-English cheat sheet with worked examples. It is educational only and not medical advice, and every number here is an illustration, not a dose — confirm your own figures with your pharmacist.
1 mg = 1000 mcg. That’s the whole rule — and it’s the most important line on this page. Mixing up milligrams and micrograms is a 1000-fold error, which is the single most dangerous mistake in this space.
After reconstitution, concentration = vial strength ÷ water added.
Example only — illustrative, not a recommendation.
Notice the first two land on the same concentration by different routes — concentration is what matters, not the vial size alone.
On a U-100 syringe, 100 units = 1 mL, so units = volume in mL × 100. To find the volume for a dose: volume = dose ÷ concentration.
Illustrative numbers only. This does not tell you what to take.
Every step is multiplication or division — no special formula. The discipline is keeping units consistent and never confusing mg with mcg.
| You have | You want | Do this |
|---|---|---|
| mg | mcg | × 1000 |
| mcg | mg | ÷ 1000 |
| vial mg, water mL | concentration (mg/mL) | mg ÷ mL |
| dose mg, concentration | volume (mL) | dose ÷ concentration |
| volume mL | units (U-100) | × 100 |
Pepathary’s reconstitution calculator runs exactly these conversions for the numbers you enter and shows its work in plain English, including both mg and mcg so you can catch a slipped decimal. It is a mixing-math tool — it never chooses a dose, and every result should be double-checked and confirmed with your pharmacist.
1 mg equals 1000 mcg. This conversion is the most common source of serious dosing errors, so it is worth committing to memory: milligrams to micrograms is always times 1000.
Divide the vial strength by the volume of water you added. A 10 mg vial plus 2 mL of water is 5 mg per mL. These are illustrative figures; confirm your own with a pharmacist.
First find the volume: dose divided by concentration. Then, on a U-100 syringe, multiply the volume in mL by 100 to get units. Pepathary’s free calculator does this for you and shows the steps.
Because it is a 1000-fold error. Treating 0.5 mg as 0.5 mcg (or vice versa) changes the amount by a factor of a thousand. Always confirm which unit a number is in before drawing anything.
No. Pepathary does arithmetic on numbers you enter — vial strength, water, and the dose your prescriber gave you. It never recommends what to take; dosing decisions belong with your physician or pharmacist.