Back in 2004 before I knew I had crohn's (before I was having HUGE stomach issues) I was so severely anemic that at my lowest point my hemaglobin was 5.6 (11-13 being "normal"). I had tried several oral iron supplements. At one point I was up to like 1200mg a day by pill...YUCK!! I finally got a 1 time IV treatment that was 5 hours long (1 hour "test" infusion then as long as no reaction within that hour they started the 4 hour infusion). It helped boost my level back up to like 11 within 2 weeks and I was better able to maintain it with diet and pills. In 2006 I got a 5 week round of IV infusions (1 hour each I think) when I was at my worst with crohn's and that also helped bring it back up from 7 to 13 over that 5 week period. It was a bigger pain in the butt cause it took 5 weeks but still worked.