iron deficiency anemia and supplements

so I'm 6mo PP, and suffer a moderately severe case of anemia, (iron stores 8). I had been taking my prenatals on advice of my doctor for about a month before this lab was taken.

so the nurse calls, and says,

n- " you're anemic, nbd, take some multivitamin/prenatal"

me- "um, I have been?"

n- "oh. okay. maybe an iron supplement?"

end convo. no time frame or dosage given.

so, I've been taking an iron supplement on top of my prenatal. well, now I'm terrified of OD'ing on iron.

how much is too much? am I being dumb?

should I call this Dr back?