mg, mcg and IU Conversions for Peptides (with Converter)
Peptide amounts are written in milligrams (mg), micrograms (mcg or µg) and sometimes international units (IU). Mixing them up is one of the most common sources of tenfold and thousandfold errors, so it is worth getting the arithmetic exactly right.
Milligrams and micrograms
1 mg = 1,000 mcg. To go from mg to mcg multiply by 1,000; from mcg to mg divide by 1,000.
| mg | mcg |
|---|---|
| 0.1 | 100 |
| 0.25 | 250 |
| 0.5 | 500 |
| 1 | 1,000 |
| 2 | 2,000 |
| 2.5 | 2,500 |
| 5 | 5,000 |
| 10 | 10,000 |
International units (IU)
An IU measures biological activity against a reference standard, not mass, so there is no universal mg-to-IU conversion. Each substance has its own factor, and some have none that applies across products:
| Substance | Conversion |
|---|---|
| Human insulin | 1 IU ≈ 0.0347 mg (34.7 mcg); 1 mg ≈ 28.8 IU |
| Somatropin (HGH) | 1 mg ≈ 3 IU |
| hCG | No fixed factor; potency varies by product, so use the IU on the label |
Insulin analogues are labelled in units that are designed to match human insulin's activity, not its mass. Always use the unit printed on the specific product.
Concentration after reconstitution
Lyophilized (freeze-dried) peptides are dissolved in a known volume of liquid. The resulting concentration is simply amount ÷ volume. For example, 10 mg dissolved in 2 mL is 5 mg/mL, which is 5,000 mcg/mL or 50 mcg per 0.01 mL.
On a U-100 insulin syringe, 100 units equal 1 mL, so one unit mark is 0.01 mL. That is why concentration per 0.01 mL is a convenient figure to check. The reconstitution calculator also converts a target amount into mL and syringe units.
This converter checks arithmetic only. It is not medical advice, and research-use products are not intended for human use. Follow the prescribing information for any medication you use.
FAQ
How many mcg are in 1 mg?
1 mg equals 1,000 mcg.
How do I convert mg to IU?
There is no universal conversion because IU measures biological activity. Each substance has its own factor; for example somatropin is about 3 IU per mg and human insulin about 28.8 IU per mg.
How do I calculate concentration after reconstitution?
Divide the amount in the vial by the volume of liquid added. 10 mg in 2 mL is 5 mg/mL, or 50 mcg per 0.01 mL.