HCG hormone is measured in international units (IU). I have also come accross measurements in mIU. Is there a conversion factor that applies, or are they the same unit? I checked wikipedia, and called several pharmacists . No one knows.
However, conventionally HCG levels are given in terms of concentration e.g international units per litre: IU/L. Slightly confusingly, both IU/L and mIU/mL are in common use. Since one mL is 1/1000 of a litre, the two factors cancel, so 1 IU/L = 1 mIU/mL.