Why does someone become anaemic?

[ChubbyScotsBurd]

My friend has been diagnosed with anaemia and put on iron tablets - I'm just wondering if it's 'just one of those things' - her diet's OK and no known gynae probs.

not eating enough iron can caused to become anaemic

She drinks loads of tea, am I right in thinking it hinders iron uptake?

My iron supplements do say not to drink caffeine an hour before and after taking them. My blood test showed up that I was anaemic a few months ago. I think I've always been borderline - never been able to donate blood. Weirdly enough my iron levels have always been better when pregnant.