international unit

noun

, Pharmacology.

1. an internationally agreed upon standard, as measured by bioassay, to which samples of a substance, as a drug or hormone, are compared to ascertain their relative potency.
2. the particular quantity of such a substance, which causes a specific biological effect. : IU

international unit

1. A unit for measuring a biologically active substance, such as a hormone or vitamin.

Word History and Origins

Origin of international unit¹

First recorded in 1920–25