So many things could be causing this. I have noticed a few folks comment, in their early days on Metformin, that they had itchy skin, although I don't recall anyone particularly having an issue with their erm,....crown jewels. I can't tell from your profile information doesn't give me any clues.
Hello @PeterGC - I've heard about this before; if you go to the main Diabetes.co.uk site there is information there about the common symptoms of diabetes. Click on the "Home" tab at the top of the page, and that will take you to the main site. The is some info under "Diabetes Symptoms" and this includes genital itching that is diabetes related, but also a range of other possible causes. Hope this helps.