While I'm not diabetic, I am lactose intolerant. You can buy lactase supplements (drops or tablets) that will get rid of the lactose, or you can buy milk that's already lactose free. It's substantially more expensive, but on the other hand, it will last a LONG time in the fridge, since when milk goes bad, the lactose is converted by lactic acid.
Mark
You might want to try buttermilk. http://www.telusplanet.net/public/ekende/lactose.htm
I stir in a little salt and pepper. Love it.