I am in the middle of a set of venofer infusions of iron right now. It depends on the quantity/dosage as to how long it takes. I get 250ml and it's infused at 200ml/hr so it takes an hour and 15 mins. I don't get a benadryl pre-med for the iron and I've never had any kind of reaction. This is my 3rd time getting iron by IV because my body doesn't absorb in pill form...probably from the crohn's. It takes several weeks (at least in my experience) for the iron to "kick in" and make you feel better. My nasty headaches are gone after 3 weeks from my 1st infusion and I'm starting to get some energy back.