A proper glucose range should be between 80-120, this is the correct range for people. Just because a blood sugar may drift to 140 or so and then go back down doesn't mean you are a diabetic.
A type one diabetic target range is usually 80-140 (For teenagers and adults)
My target range is 80-140, and I'm terrible at managing.
If you are a diabetic, it's best to treat a bloodsugar above 180, and below 80 or 70.