Yes, I do find it very difficult to concentrate, and think really, when I'm in double figures. So I work hard to avoid getting up there and if I find my self up there I correct.
Focus - I play video games in my spare time. Being at e.g. 12 vs 6 is a matter of finishing last or first (literally). The difference in the ability to focus is ginormous.
Absolutely! and if you're frequently running high you may stop noticing the affect and it becomes the norm for you. It was for me. Now I'm much sharper in the brain, more cheerful, more... me!
I live with this issue on a minute by minute basis! It makes me feel like not eating, which usually results in my eating anyway and feeling my body go sluggish. I also feel guilty when this happens during work because my work is not the same.
Took me a while to realise that when I feel depressed or particularly when I feel suicidal I should be testing my blood sugar and correcting accordingly
Maybe if you're REALLY high. but 10-11 I don't think it would affect mentation especially if it were temporary. It might be more psychological rather than physical/chemical.