Hemoglobin A1c Test (HbA1c, A1c, Hb1c)

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: John P. Cunha, DO, FACOEP
    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.

Complications of Uncontrolled Blood Sugar in Diabetes

In type 1 and type 2 diabetes, uncontrolled blood sugar can lead to a number of associated complications, for example:

  • Foot problems
  • Urological and sexual problems (urinary tract infections [UTIs], erectile dysfunction [ED]
  • Yeast infections
  • Heart disease
  • Kidney disease
  • Diabetic neuropathy
  • Diabetic eye disease

Hemoglobin A1c definition and facts

  • Hemoglobin A1c is a protein on the surface of red blood cells that sugar molecules stick to, usually for the life of the red blood cell (about three months).
  • The higher the level of glucose in the blood, the higher the level of hemoglobin A1c is detectable on red blood cells.
  • Hemoglobin A1c levels correlate with average levels of glucose in the blood over an approximately three-month time period.
  • Normal ranges for hemoglobin A1c in people without diabetes is about 4% to 5.9%. People with diabetes with poor glucose control have hemoglobin A1c levels above 7%.
  • Hemoglobin A1c levels are routinely used to determine blood sugar control over time in people with diabetes.
  • Decreasing hemoglobin A1c levels by 1% may decrease the risk of microvascular complications (for example, diabetic eye, nerve, or kidney disease) by 10%.
  • Hemoglobin A1c levels should be checked, according to the American Diabetic Association, every six months in individuals with stable blood sugar control, and every three months if the person is trying to establish stable blood sugar control.
  • Hemoglobin A1c has many other names such as glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin, and HbA1c.

What is a hemoglobin A1c?

To explain what hemoglobin A1c is, think in simple terms. Sugar sticks to things, and when it has been stuck to something for a long time it's harder to the get sugar (glucose) off. In the body, sugar sticks too, particularly to proteins. The red blood cells that circulate in the body live for about three months before they die. When sugar (glucose) sticks to these red blood cells by binding to hemoglobin A1c, it gives us an idea of how much glucose has been around in the blood for the preceding three months. Hemoglobin A1c is a minor component of hemoglobin to which glucose binds. Hemoglobin A1c levels depend on blood glucose concentrations. The higher the sugar concentration in the blood, the higher the detectable hemoglobin A1c levels. At any point in time, hemoglobin A1c levels represent the average blood sugar concentrations in the person with diabetes for approximately the preceding 3 months.

What makes a person's hemoglobin A1c levels high or low?

Hemoglobin A1c levels can be altered by

  • oral or IV glucose intake,
  • fasting,
  • use of insulin, and
  • by combinations of these and other factors.

The goal for people with diabetes, with their doctor's help, is to establish stable blood glucose levels resulting in hemoglobin A1c levels that are at least below 7% to reduce or stop complications of diabetes (for example, diabetic nerve, eye, and kidney disease).

Medically Reviewed by a Doctor on 8/30/2016

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