Iron supplements for frequent blood donors

I donated in November, January, and two days ago. On the most recent donation my iron test came in at the bare minimum (13.0) and I had trouble getting out of bed Friday and Saturday morning.

The Red Cross literature recommended taking an iron supplement if you donate three or more times per year, but also mentioned consulting a physician before taking an iron supplement. Do I need to see a doctor (which I haven't done since the Clinton administration)? Or is that just a CYA, and I should start taking iron?

Also, is there a particular brand I should use or avoid, or are they all basically the same?