Im similar to Helen, except my levels arent low enough to be called anaemic.
I went to the docs cause i was getting fed up of feeling dizzy every time i stood up, or was stood in the same spot for more than 30 seconds (made washing up fun!) and had blood tests. They noticed my folic acid levels were little low, had few tablets and it made me 99% better!
Could be withdrawl symptomes to caffine or sugar though, although i tend to get headaches rather than dizziness x