Depends on what vitamins you speak of. Vitamins A,D,E,K, metals (iron, chromium, copper, etc) can be OD so take into account the vitamins you get from foods and the ones you take as vitamins. Whole wheats, if voer consumed, can affect your bowel movements and stomach so ease yourself into it.
Vitamins B and C are water soluable, so anything left over will be spilled into the urine. For those of you that take B complex, your urine will almost take on a freakish neon yellow color. This is normal and kinda cool to see.