I want to, but I don't have time to read all the other responses right now.
I was diagnosed when I was 6 (now I'm 25) so I know all about rebellion and diabetes!
Diabetes is all about control. Whether it seems like it or not, your son DOES know the consequences of his actions, he knows how it doesn't feel good to have higher sugars, and most importantly (almost exclusively) he knows exactly how it drives you crazy.
What's likely going through his head is "Man, my momma is being annoying! [I love her and always will], but Damn is she a nag! I've had diabetes for like 10 years now, and she STILL doesn't trust me to take care of myself? Anyway, I just tested and my sugars are 250, Yuck, I feel terrible. On the one hand, I could take a correction and feel better in a bit, but how much more independent would I feel if I could just show her that no matter how much she nags [and helps, and supports, and is always there for me and loves me], I will fundamentally always be in control. I am the one with this disease attached to his body - day and night. [ I know that it effects her just as much as me emotionally and that she's devoted just as much time, if not more than me to taking the best control of it, but heck, I'm almost a teenager - it has to be all about ME!"
Ok, so that is a pretty opinionated quote, and I'm not suggesting that your child has malice towards you, not at all! I'm betting a fair chunk on the likeliness that he just wants to feel like he's in total control. At the same time, he needs to feel like he can come to you for help when he needs it. Basically, he needs to feel like you trust him.
Talk to him, not about diabetes, but about independence and ask him what he needs to feel like he has enough freedom. From there, make a compromise and he will too.
Thinking back, my parents made this kind of shift with me. They explained that fundamentally, how I controlled my diabetes effected me and not them. Because they stopped insisting on seeing my logbook all the time, I stopped hiding it. Before, I needed to feel that I was the only one who could see it unless I gave it to them. When they stopped requiring me to show it to them, I was more likely to leave it lying on the kitchen table or something where it was more public.
Anyway, I empathize with your situation. It's tough for both sides of the equation. I wish you and your son all the best!