@turquoise-- Actually, results of lab glucose tests with blood drawn from the vein are the most accurate.
I asked my endocrinologist about this one time, if the results of glucometer readings and the ones from the hospital labs are the same. And she said that the labs give more accurate results because the blood is drawn directly from the vein. There could be up to 20mg/dl difference between a glucometer reading and a lab reading.
Because of this, she told me to make sure that I go in for a a1c test every three months. This gives the average blood glucose levels for the past three months. So if there is an inaccuracy in the glucometer, you will probably find out when the results come back too high or low. I also make sure that my test strips are not expired because that can give inaccurate results too.