What Is The Cause And Treatment For Low Iron Level?

My daughter has been diganosed with low iron level, I believe its 140 and I think it should be 280? She is only 16 and seems sensitive to all drugs. She had glandular fever last year and has not been right since. She got glandular after she was prescribed racoutane for her skin, worse mistake ever to take this drug. She was a top athlete and hockey player and has not been anywhere near herself for the past year. I am very confused with the present situation as she is not anaemic? Therefore a friend has suggested I get a print out from my doctor of all her recent blood checks to see if she if B12 deficient? I have only spoken with our doctor over the phone and have yet to assertain whether it is B12? or what exactly is wrong? Do you have any ideas as to what I should do to get her back to full health, it is very frustrating, she is really tired and not at all her old self, her studies (she is very bright) and sport have suffered greatly over the past year.?