Low Ferritin?

kmpage28

At DD one year appointment her CBC showed anemia (nothing too drastic, but was low) and low ferritin level.  Pedi has us start her on Poly-Vi-Sol with Iron.  Just had her labs re-tested at her 15 month appointment and her Ferritin is still low (also still anemic, but numbers are improving).  Anyone else go through this?  Any other suggestions?  Our pedi doesn't seem overly worried at this point but as her Mommy, it is a bit harder not to worry...