international unit of vitamin A

international unit of vitamin A
an older unit of vitamin A activity, equal to the activity of 0.3 microgram retinol or 0.6 microgram β-carotene; because the provitamin A carotenoids are absorbed less efficiently than is retinol, the source must be specified. Although largely supplanted by retinol equivalent (q.v.), the unit is still used in labeling. When the source is retinol, the unit is officially vitamin A u.

Medical dictionary. 2011.

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  • International unit — In pharmacology, the International Unit is a unit of measurement for the amount of a substance, based on biological activity or effect. It is abbreviated as IU, as UI (Spanish unidad internacional or French unité internationale or Italian unità… …   Wikipedia

  • international unit — Pharm. 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… …   Universalium

  • international unit — (IU)    a unit used to measure the activity (that is, the effect) of many vitamins and drugs. For each substance to which this unit applies, there is an international agreement specifying the biological effect expected with a dose of 1 IU. Other… …   Dictionary of units of measurement

  • international unit — noun a unit of activity for a particular vitamin, hormone, etc. in terms of the activity of a standard quantity …   English new terms dictionary

  • international unit — /ɪntəˌnæʃnəl ˈjunət/ (say intuh.nashnuhl yoohnuht) noun a unit of the amount of a biologically active substance, such as a vitamin or hormone, required to produce a specific response …  

  • international unit — noun Date: 1922 a quantity of a biologically active substance (as a vitamin) that produces a particular biological effect agreed upon as an international standard …   New Collegiate Dictionary

  • international unit — noun : a quantity of a biological (as a vitamin, hormone, antibiotic, antitoxin) or its equivalent based on bioassay that produces a particular biological effect agreed upon internationally …   Useful english dictionary

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