Personally, I think it is best to take a quality multi vit/mineral complex, rather than singular nutrients for the synergistic effect...
I take a prenatal vitamin because they are very strong...I like Rainbow Light because it has Iodine (from kelp). BTW, I have a history of anemia and the prenatal vits have always cured this condition for me.
I think the one-a-day type is best because most can only remember to take it once per day!
I also think it is a bunch of BS that iron should be taken alone, because I have tried both ways and I actually find that the multi works best.
Vit C has a lot to do with iron obsorption, The Right C by Natures Way is what I take. Fresh oranges would really help too.
Lowering his dose, or simply taking a week off, is for the best. let his body catch up a bit, to bring his anti-oxidant reserves back up.
Perhaps then he can get on a moderate maintenance dose of 6 drops at bedtime.