mIUmL

mIU/mL stands for milli-International Units per milliliter and is a concentration unit used in medicine and laboratory science. It expresses the amount of a substance’s biological activity or potency present in one milliliter of a solution. The unit is commonly used for hormones, enzymes, and other biologically active substances measured in blood or other fluids.

The International Unit (IU) is a biological activity-based measurement defined for each substance by pharmacopeial authorities. Because the IU reflects potency rather than mass, the mass corresponding to a given number of IUs varies from substance to substance. Therefore, 1 mIU/mL denotes one thousandth of an International Unit per milliliter for that specific substance, and, in terms of per-liter concentration, equals 1 IU/L.

Common substances reported in mIU/mL include hormones such as human chorionic gonadotropin (hCG) for pregnancy testing and fertility monitoring, and other analytes like insulin, thyroid-stimulating hormone (TSH) in related units, and various enzymes in clinical panels. In some contexts, results are reported in mIU/L, which is equivalent to mIU/mL multiplied by a factor of 1,000, reflecting the same concentration expressed in different volumetric units.

Interpretation of mIU/mL results depends on the specific assay and the laboratory’s reference ranges. Because the IU is defined per substance, direct comparisons across different substances require substance-specific calibration and conversion data. In practice, clinicians interpret mIU/mL values within the context of the assay method and clinical guidelines.