mg, mcg, IU and syringe “units” — what each means, how they relate, and a worked example.
The trickiest part of working with peptides is that several different units are in play at once — the mass in the vial, the dose you want, and the marks on a syringe. These are not the same thing, and mixing them up is the most common source of error.
This guide untangles them, then shows a worked example.
Milligram — the mass of peptide in the vial (e.g. a “10 mg” vial).
Microgram. 1 mg = 1000 mcg. The common unit for a dose.
Millilitre — volume of liquid, e.g. the bacteriostatic water added.
International Unit — an activity-based unit used for some compounds such as HGH.
The tick marks on an insulin syringe (100 marks = 1 mL). Not equal to mg.
| From | To | Rule |
|---|---|---|
| mg | mcg | × 1000 |
| Concentration | mg per mL | vial mg ÷ water mL |
| Syringe “units” | mL | units ÷ 100 |
| Dose per mark | mcg | (mg/mL) × (units÷100) × 1000 |
No. A “unit” is a volume mark on an insulin syringe (100 units = 1 mL). How much peptide sits in one unit depends entirely on your concentration.
An International Unit measures biological activity rather than mass, used for certain compounds like HGH. It does not convert directly to mg without a compound-specific factor.
No — the peptide mass stays the same. More water just spreads it across a larger volume, lowering the concentration.
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