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Hemoglobin Levels (cont.)

What Is the Hemoglobin A1c Test?

The hemoglobin A1c test is a measure of the approximate glucose level that occurred in a person (usually a person with diabetes) over about a 3 month period by determining the person's per cent of hemoglobin A1c. Hemoglobin A1c is also known as glycated hemoglobin; it is a form of hemoglobin made upon exposure of hemoglobin in the blood stream to glucose.

  • Hemoglobin A1c test is based on the fact that as blood sugar (glucose) increases, more sugar is bound to hemoglobin, and more glycated hemoglobin is formed.
  • Hemoglobin A1c concentration is related to the average amount of glucose in the blood over about 3 months. Normal amounts of hemoglobin A1c are about 4%–5.9%.
  • Hemoglobin A1c at 6% correlates to an average glucose level over 3 months of 135 mg/dl.
  • Often, the recommended goal for a person with diabetes is 6.5% hemoglobin A1c (representing a glucose level of 152.5 mg/dl on average).
  • Each 1% above 6% hemoglobin A1c represents an increase of 35 mg/dl of glucose.
  • Consequently, detecting an 8% concentration of hemoglobin A1c would equal a glucose level of 135 plus 70, or 205 mg/dl average over 3 months.
  • Concentrations of 8% or more indicate poor glucose control.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


Nabili, Siamak N. MD, MPH. "Complete Blood Count." Updated Jan 24, 2014.

Davis, Charles Patrick MD, PhD. "Hemoglobin." Nov 4, 2015.

"Hemoglobin A1c." Updated Apr 24, 2002.

Medically Reviewed by a Doctor on 11/20/2017

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