Have you tested this? What formula are you using?
I have not had a chance since I have only been diagnosed for less than three months. The formula I am using is one that I came up with using the Nathan formula to calculate average blood glucose level from HbA1c that I found in the internet. Since I wanted to calculate HbA1c and I had the information about my blood glucose levels, I just used some high-school algebra to work it back. As you can see, I was wrong when I said that I would never use that stuff in real life. The actual formula is (Average mg/dl + 86) / 33.3.
FORMULA: HbA1c =( mg/dl + 86) / 33.3
( HbA1c X 33.3 – 86 ) = Mean Blood Glucose (mg/dl)
descarcare document: http://www.loanuniverse.com/Diabetes/