Do multivitamin tablets cause changes in stool colour? Been taking them for about three weeks now, but since yesterday have had diarrhoea / sickness and my stools are the same colour as gearbox oil (i.e. a very dark brown, almost black, my vomit was the same).
Before I trouble my GP want to make sure this is what it could be, before I start worrying about other ailments that might cause it?