What is causing me to have Iron deficiant anemia?

I am almost 2 years post op and my blood work came back with a low hemoglobin levels. The doctor said I have Iron deficiancy anemia. I am waiting to hear back from her. What am I doing wrong? I take vitamins and B-12. What else should I be doing?

We greatly appreciate your interest in helping us build our Q&A database. To discourage vandals from posting garbage, however, we require people to register before posting.