How to convert between mg, mcg, IU, and syringe units — with worked examples for the most common peptide concentrations.
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The single biggest source of peptide dosing errors is unit confusion — reading "250 mcg" and drawing the equivalent of 2500 mcg because someone mixed milligrams and micrograms. The math is simple once you see it; this guide exists so you don't have to reinvent it every time.
You always start with two numbers:
Dividing gives you concentration in mg/mL. Multiply by 1000 for mcg/mL.
You have three numbers to connect:
Volume in mL = target dose ÷ concentration.
Multiply by 100 to get syringe units (since 1 mL = 100 units on a standard insulin syringe).
The concentration you choose directly affects how accurately you can dose. A concentration that puts your typical dose at 10–30 syringe units is the sweet spot — coarse enough to read reliably, fine enough that small variations don't meaningfully change the dose.
| Typical dose | Good units per dose | Poor units per dose |
|---|---|---|
| 100 mcg | 10–20 | Under 5, over 60 |
| 250 mcg | 10–25 | Under 5, over 70 |
| 500 mcg | 15–50 | Under 10 |
| 1 mg | 25–75 | Under 15 |