Can a dog really sense diabetes?

I realize it's a popular contention that some dogs are able to detect low blood sugar by smelling something about a person and signal when that person is about to have a diabetic episode of some sort. I'm well aware that dogs have very good senses of smell. Nevertheless, this strikes me as somewhere between "improbable" and "dubious," because the change in someone's breath or sweat caused by low blood sugar seems as though it would be similar to all sorts of other ordinary, non-diabetic bodily fluctuations that occur throughout the course of a day.

It also strikes me as improbable that someone's own pet who happens to be an adorable and lovable dog would just happen to possess this ability. And they way the animal is supposed to signal the onset of a diabetic attack is usually to lick and kiss the human, which is similar to how the animal would behave if it were requesting food or treats or attention the way an ordinary household pet would.

But if there's some actual evidence of this out there, my mind could be changed. Show me the evidence, change my mind!