Cereal before 6 months???
Now if you baby is showing signs of low iron, it would be worth getting the babe tested, but it sounds like this is just a general recommendation from your pediatrician.
I am really surprised to hear about the Candian rec. The American Academy of Pediatrics backed off the cereal recommendation twenty years ago. Solids are recommended after six months and unless you have a dinosaur they suggest real foods. BF are routinely recommended to take an iron supplement but I don't because the research that supports it is lame. (see kellymom.com) I do take an iron supplement personally and if my baby was shown to have low iron via a blood prick we would provide supplementation.
Besides, cereal is a lousy source for iron. Heme iron, like that in bm or meat, is much more easily absorbed. Many authorities now recommend the earlier introduction of heme sources.