Which vitamins are harmful if taken to much?

All are harmful if taken in excess.

The quantities needed of each vitamin vary , vitamin by vitamin .

Vitamins are only needed to stimulate various responses in the human organism. Thereby only small amounts are needed.

It a bit like a bricklayer, with a trowell, mortart and bricks. The torwell is only a small tool,, but it can put together a lot of mortar and bricks. So the trowell is equivalaent to the vitamin. A small item can do a lot of work.