Unless you've had problems in the past I think you'll be fine. I am a 25 year old type 1 and have both arms tattooed and have had several piercings in the past, and have never, ever had any issues. It really boils down to how well you care for the piercing. In my experience a lot of people are scared (or are just unaware of actually how to) clean a new piercing. My advice is to buy some 'wound wash' type spray from Boots/Superdrug and liberally spray it twice a day, then remove any gunk with a cotton bud. There is no need to actually touch the piercing or jewelery itself, and doing this will lead to irritation and infection, diabetes or no diabetes. Hope this helps!