I have taken iron supplements in the past, most recently metagenics hemagenics.
Besides being slightly nauseating it caused stains on my top two teeth. They were easily removed at the dentist.
Now my practitioner wants me to take it again and I am not really wanting to due to the stains it causes.
She didn't think that the iron caused the stains, but that it had to do with calcium. In searching the internet all I can find is that it does cause stains, not why.