I've mentioned this in my earlier blog about "Sessions" and it seems others have experienced low iron levels. I was also talking to another lady at running club tonight who has had similar problems. This link may be of interest:
I found it quite useful - when I had the contraceptive injection I was told that it would be advisable to take a calcium supplement as I hate milk, even in tea or coffee, and the injection can have a detrimental effect on your bones. I've been taking my calcium supplement at the same time as my iron supplement - I now know that the calcium can stop the iron being properly absorbed and can make sure I take them at totally different times.