Well I can't say definitely that my diabetes makes me itchy but something does...
For the last few years (prior to being diabetic I've occasionally had terrible itching in my ears (feels as if something creepy crawly is in there - when I mentioned this to my gp he seemed to think I meant there were actually things creeping around in them and more or less said I was talking nonsense!)
But since I've had diabetes, I've also had longish spells of more or less permanent itching across the small of my back. I use Eurax cream for this and it generally keeps it under reasonable control.
Robbity
PS Leg cramps can be caused by lack of potassium, and I used to get this a lot years ago when on diuretics. My cure was to eat bananas, but can't really do that now if I get cramps, so my husband recommended his LO Salt salt which contains potassium.