I've struggled with low iron levels for years. I take iron also, but it is a balancing act between how much I need and how much I can tolerate.
I think having anemia due to low ferritin (iron) levels and low B12 levels are two different things, but your doctor can make that distinction looking at your blood work. The last time I had blood work done, I was tested for both, and it was (like it always is
) low iron.
Here is the link to the Mayo Clinic page that contains iron deficiency anemia symptoms:
http://www.mayoclinic.com/health/iron-deficiency-anemia/DS00323/DSECTION=symptoms
I'm usually really tired and irritable when my iron levels get too low. Weirdly enough, I also crave salty things like olives and tomato juice. That is a tip off for me that I need to get it checked again.