# Medical procedure - Red Blood Mass

**URL:** <https://boards.straightdope.com/t/medical-procedure-red-blood-mass/270475>\
**Category:** Factual Questions\
**Created:** [October 21, 2004, 8:10pm UTC](https://boards.straightdope.com/t/medical-procedure-red-blood-mass/270475 "2004-10-21T20:10:26Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ticker](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@ticker](https://boards.straightdope.com/u/ticker)\
**Post date:** [October 21, 2004, 8:10pm UTC](https://boards.straightdope.com/t/medical-procedure-red-blood-mass/270475/1 "2004-10-21T20:10:26Z")

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Today I was at the hospital having my Red Blood Mass checked. This involved having a sample of blood taken, tagged with a radioactive Chromium isotope, re-injected and then two more samples taken at 20 & 40 mins after injection. Presumably these two samples then have their radiation levels measured.

I am not exactly why this procedure was ordered - something to do with a very slightly elevated haemaglobin(sp?) level. I also forgot to ask (hospitals make me a little nervous) (a) What exactly is being measured and (b) how does it work.

Can any Dopers enlighten me?