# what is the conversion factor between IU and mIU?

**URL:** <https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927>\
**Category:** Factual Questions\
**Created:** [November 23, 2011, 10:54pm UTC](https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927 "2011-11-23T22:54:28Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![gonzalo\_de\_cordoba](https://avatars.discourse-cdn.com/v4/letter/g/848f3c/32.png) [@gonzalo\_de\_cordoba](https://boards.straightdope.com/u/gonzalo_de_cordoba)\
**Post date:** [November 23, 2011, 10:54pm UTC](https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927/1 "2011-11-23T22:54:28Z")

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HCG hormone is measured in international units (IU). I have also come accross measurements in mIU. Is there a conversion factor that applies, or are they the same unit? I checked wikipedia, and called several pharmacists . No one knows.

Thanks in advance.

Shon

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**Author:** ![hajario](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hajario/32/171_2.png) [@hajario](https://boards.straightdope.com/u/hajario)\
**Post date:** [November 23, 2011, 10:56pm UTC](https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927/2 "2011-11-23T22:56:25Z")

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It’s probably milliIU or 1/1000 of an IU.

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**Author:** ![Fish\_Cheer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fish_cheer/32/17179_2.png) [@Fish\_Cheer](https://boards.straightdope.com/u/Fish_Cheer)\
**Post date:** [November 23, 2011, 10:56pm UTC](https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927/3 "2011-11-23T22:56:34Z")

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Without any knowledge about HCG, I’d assume that the lower-case “m” is an [SI prefix](http://en.wikipedia.org/wiki/SI_prefix). One mIU would then be 0.001 IU.

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**Author:** ![rekkah](https://avatars.discourse-cdn.com/v4/letter/r/ee59a6/32.png) [@rekkah](https://boards.straightdope.com/u/rekkah)\
**Post date:** [November 23, 2011, 11:17pm UTC](https://boards.straightdope.com/t/what-is-the-conversion-factor-between-iu-and-miu/603927/4 "2011-11-23T23:17:08Z")

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One mIU is indeed 1/1000 of an IU.

However, conventionally HCG levels are given in terms of concentration e.g international units per litre: IU/L. Slightly confusingly, both IU/L and mIU/mL are in common use. Since one mL is 1/1000 of a litre, the two factors cancel, so 1 IU/L = 1 mIU/mL.