A1C and You — Essential Facts

A1C Explained

A1C stands for hemoglobin A1C.1 Hemoglobin is the protein in red blood cells that carries oxygen to all the tissues of your body.1 Glucose in the bloodstream attaches to hemoglobin molecules, producing glycosylated hemoglobin, or A1C.1 Glucose stays attached to glycosylated hemoglobin for the life of the red blood cell, about 4 months.1 A1C is measured as a percentage of total hemoglobin.1

Therefore, A1C measures your average blood glucose over the entire previous 3 months, 24 hours a day.1 It includes both fasting blood glucose and values after meals. A1C values are in contrast to blood glucose values from self monitoring, which measure your blood glucose at the time you perform the test.

Relation of A1C to daily blood glucose levels

A1C both provides a 3-month average of daily blood glucose levels and accurately reflects the range of daily blood glucose values (See A1C and average blood glucose comparison).2,3 Higher blood glucose monitoring results mean higher A1C levels. Both measures together provide a complete picture of blood glucose control.1 It is therefore important to focus on both blood glucose and A1C levels to improve diabetes control.

A1C and average blood glucose comparison

A1C and average blood glucose comparison

Meaning of different A1C values

For a person without diabetes, experts generally agree that normal A1C values fall between 4% and 6%.4 Target A1C levels for people with diabetes are below 7%,5 and as close to non-diabetic levels as possible. Levels above 7% are considered elevated,5 and levels above 8% indicate the need for a change in diabetes management.1

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References:

  1. The ABCs of hemoglobin A1C testing. Diabetes Monitor 1/6/2010. Available at http://www.diabetesmonitor.com/b59.htm. Accessed November 18, 2010.
  2. Rohlfing CL, Wiedmeyer H-M, Little RR, England JD, Tennill A, Goldstein DE. Defining the relationship between plasma glucose and A1C. Diabetes Care 2002;25:275–78
  3. Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ, for the A1C-derived Average Glucose (ADAG) Study Group. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31:1473–8.
  4. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2008 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes 2008;32(suppl 1):S30
  5. Beyond blood sugar: Testing A1c. MedicineNet.com. Available at http://www.medicinenet.com/script/main/art.asp?articlekey=52041. Accessed March 15, 2011.