Iron? (women)

toothpastechica

For most of my life I have struggled with low iron. As an adult I have started taking womens 1 a day which contains 10mg of iron. Because I am low I decided to switch out counting sugars for iron on my food logging, but I have a couple questions.
1. How is it measured for logging? Is it mg? g? When I logged my multivitamin to see, it said 58, but I have no idea what that 58 means to even know if its correct or not.
2. If I get enough iron from other sources (according to MFP I have lots of iron today in my diet alone), should I still be taking my multivitamin? I have heard over and over that too much iron isn't good for you either, and some days that vitamin pushes my iron over what mfp says is the daily goal.