Answer:
The time between daylight and darkness when blood drinkers like to come out
When I am caught I am thrown away. When I escape you itch all day.
I begin and have no end. Eventually I will be the end of all that has begun.
I am not a toy though many use me for pleasure. I have a butt but I cannot poo.
I am the building with the most number of stories.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.