- 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.
- the particular quantity of such a substance, which causes a specific biological effect. Abbreviation: IU
Origin of international unit
First recorded in 1920–25
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- The quantity of a biologically active substance, such as a hormone or vitamin, required to produce a specific response.
- A unit of potency for similarly active substances, based on this quantity and accepted as an international standard.
- A unit for measuring a biologically active substance, such as a hormone or vitamin.