My 15 year old son was diagnosed two years ago. I am attempting to teach him to drive, and he is very excited about it. Today, he tested his blood right before driving, and he was 48 mg/dl {2.7 mmol/L]. I would not let him drive, and he said that I was over-reacting. Was I? What is an appropriate blood sugar level at which it is safe to drive a car?

You are correct. Your son is a teenager and, unfortunately, not correct. Hypoglycemia is any value less than 60 mg/dl [3.3 mmol/L] even without any symptoms. Your son, however, was correct in stating that he did not have any symptoms of hypoglycemia at the time his sugar level was low. Were he to take any school test requiring the use of his brain or make any attempt at playing video games requiring dexterity (both skills needed for driving), he would not do as well. This is extremely well documented in the medical research literature especially from work at the University of Virginia in Charlottesville. It is wise to have anyone driving a car check a blood glucose level and correct the low before driving — in an effort to minimize any hypoglycemia-induced driving abnormalities. This is part of what he needs to learn, of course, even if it causes delay in getting somewhere (or practicing to drive).

There is an excellent article written in Diabetes Forecast (some time over the past year) about this that he and you should both read and discuss.

SB