I have one of my quarterly visits to the Barbara Davis Center coming up, and as a result I need to collect a couple of samples of my overnight liver for them. My doctor does these tests once a year or so to make sure my kidney is still functioning normally.
I was actually supposed to do this for my last doctor's appointment, but I forgot. Basically, I need to collect all my urine overnight and in the morning in one of those little plastic "hats" they use in the hospital to measure your urine. (For me, this means peeing in the hat just once in the morning, since I don't drink enough fluids to have to get up to pee in the middle of the night.) Then I pour a little bit of the urine into a little vial to take back to the doctor's office with me, and discard the rest.
Since my doctor wants two samples, I need to do this twice.
Kidney failure is a common problem for diabetics, presumably because the kidneys have to work harder in a person with diabetes: Any time the person's blood sugar is over 180, their kidneys kick into overdrive in order to filter out the excess sugar. However, this page about kidney disease claims that it can happen even in diabetics whose sugars are under tight control.