Home / Tools / Peptide dose calculator: how many units to draw

How the calculation works

1. Concentration = peptide in the vial (mg) ÷ water added (mL)
2. Volume = prescribed dose (mg) ÷ concentration (mg/mL)
3. Units = volume (mL) × 100 on a U-100 syringe

Worked example with made-up numbers: a 10 mg vial mixed with 2 mL of water is 5 mg/mL. A prescribed 2.5 mg is 2.5 ÷ 5 = 0.5 mL, which is 50 units on a U-100 syringe. If the dose is written in mcg, divide by 1,000 first: 500 mcg is 0.5 mg.

The mistakes that cause wrong doses

• mg versus mcg. A thousand-fold difference. Check the unit on the prescription and on the vial.
• Forgetting how much water went in. Write it on the vial or save it somewhere the day you mix it.
• Wrong syringe. Units only mean something on the syringe they were worked out for. Most insulin syringes are U-100, but check yours.
• Redoing the maths from memory weeks later. The calculation is easy once. It is easy to get wrong on a tired evening.

If the result is tiny (under 2 units) or more than the syringe holds, stop and check the inputs, then ask your pharmacist or prescriber before injecting.

Let the app keep doing this

A web calculator forgets your vial the moment you close the tab. In PepLevel you save each vial or pen once: how much it holds and how much water went in, or the strength on the label. From then on, every planned dose from your prescriber's plan shows its volume in mL (cc in the US), and in syringe units if you enter the scale, on Today, on the medication page and when you log the dose. The app also tracks what is left in the vial and reminds you before you run out. Like this page, it only converts the dose you were given. It never works out what your dose should be.

Common questions

How many units is 1 mL on an insulin syringe?

On a U-100 insulin syringe, 1 mL is 100 units, so 0.1 mL is 10 units. Other syringe types use different scales, so check the one you have.

How do I convert mcg to units?

First convert mcg to mg by dividing by 1,000. Divide that by the vial concentration in mg/mL to get mL, then multiply by 100 for U-100 syringe units.

Does this calculator tell me what dose to take?

No. It only converts a dose your prescriber has already set into a volume. The dose itself must come from your prescriber and the product information.

PepLevel does this from your own doses

Saved vials, planned doses in mL, and a level curve built from what you actually logged. Coming soon to the App Store.

Get PepLevel