Being "high" could delay you realization that you are having a diabetic attack(IE: low blood sugars) and if you are not used to low blood sugars, you may not realize them till they are too late.
But also the urge to eat is also another problem, you may eat and eat, but with the "dry mouth (cotton mouth)" you may feel the urge to eat more, thus increasing you'r blood sugars to a very high amount.
Be carfull is all I can say. =)
Impair your judgement, meaning you might not realize you are having a low blood sugar or you might forget if you gave your shot or tested your blood sugar. All of those things are very important to maintaining your health. I am not trying to sound preachy, but anything mind altering can make you prone to bad choices and as diabetics we don't have much room for bad choices. Not to mention how bad it is for your lungs, which is bad for your cirulation, which as diabetics we have to be careful of all those things because they can lead to complications later on in life. Do I sound like a broken record! Please just be very careful whatever you do--maybe others have some other advice for you too.