However, there are known inconsistencies with the lab tests and their interpretation, and levels can vary up to 1% among individuals regardless of the glycemic index of the foods consumed. HbA1c is a lab test that measures the number of glucose molecules attached to hemoglobin over a period of 90 - 120 days, which is expressed as a percentage, with 3 to 6% considered to be normal, and lower being better. This gives a better average of blood sugar management with diabetics since it is averaged over 2 - 3 months, in contrast to the daily high low glucose fluctuations when measuring blood sugar... Full Text