I would see your healthcare provider to make sure this isn't a medical or psychiatric condition.

Until you get to your doc you may find using hydrocortisone cream and a moisturiser will ease the itch

It could be a condition called Formication

Not directly related to Diabetes but can be brought on my Kidney or Liver disorders (which are more common in diabetics)

But it can also be caused by a whole list of medications, so you should really be discussing it with your Doctor to figure out whether it's medication, your organs or some neurological disorder causing this

Way too many options, some that could turn deadly if they aren't addressed to be sitting at home with Google trying to figure this out