international unit

noun

: a quantity of a biologically active substance (such as a vitamin) that produces a particular biological effect agreed upon as an international standard

Examples of international unit in a Sentence

Recent Examples on the Web

In this latest randomized trial, approximately 1,000 people aged 50 and older were divided into two groups — one group took 2,000 international units (IU) of vitamin D pills each day, and the other group took placebo pills. —Melissa Rudy, FOXNews.com, 29 Aug. 2025

Most adults require 600 to 800 international units (IU) of vitamin D daily. —Lindsay Curtis, Verywell Health, 5 Aug. 2025

People under 70 years old need 600 international units (IU) of vitamin D per day, while people over 70 should get 800 IU.2 Before taking a vitamin D supplement, talk to a healthcare provider for guidance. —Sherri Gordon, Health, 30 June 2025

Most experts recommend aiming for at least 800 to 1,000 international units per day. —Alisa Hrustic, SELF, 24 June 2025

Word History

First Known Use

1921, in the meaning defined above

Rhymes for international unit

• lunate
• multiunit
• subunit

Medical Definition

international unit

noun

: the amount of specific physiological activity of a standardized preparation (as of a vitamin) that is agreed upon as an international standard especially for comparison with other biologicals containing the substance in impure form or with a related biologically active substance

also : the amount of the biologically active substance in the standard amount of the preparation producing this activity