Here are two good articles on meter accuracy and blood sugar:
http://www.healthline.com/diabetesm...-sugar-levels#1
https://diatribe.org/issues/68/adams-corner


As suggested before, find a friend with a regular glucose meter (not one that also reads ketones) and check against that. I found the precision extra combo meter was off on the glucose, why some suggest you continue to take glucose with a devoted meter, and only ketones with the combo meter, and that brand is not getting good reviews for accuracy anyway. Also consider accuracy of any glucose reading in light of linked articles.