I am diabetic and maybe I am just dense, but dosen't powdered sugar have too much sugar?

I am trying to find like a good basic cake icing recipe that is sugar free, but all I have seen or the same as the ones I have made when I took a cake decorating cl. They all require 1 to 2 lbs of powdered sugar. Is there something different about it that it doesn't affect diabetics like other sugar?