iron and B vitamins (I think it's B1 - but I can't remember which "B" it is) can both make people nauseated. With iron, some forms are easier on G/I systems than others (e.g., carbonyl iron and heme iron -- there may be others, too), so you could always get a "senior" version of a multi (those usually don't contain iron - but check) and then take your iron separately. Not sure how to get around the issue if it's the B vitamin that's doing a number on you, though I guess just try a different brand?