I agree with Gerri! I have never seen it indicated from a reputable source that non-diabetics have such a wide and dangerous range. 4.0-5.9% is the normally quoted non-diabetic range, which coincidentally is what diabetics should be striving toward as well. The ADA goals of below 7% are famously high and we can all attest to that, with the AADE recommending below 6.5% - which is a good deal better.
It is important for all diabetics to understand that blood sugars over 140 mg/dL cause cellular damage. An average as high as 7.0% (or 155 mg/dL) means that we are too high over half of the time. To avoid complications, tighter goals closer to non-diabetic ranges are the true aim, ideally achieved with few hypos and a tight standard deviation from the mean.