The A1c Test

Written by Dale Kiefer | Published on July 25, 2012
Medically Reviewed by Peggy Pletcher, MS, RD, LD, CDE on May 22, 2014

Overview

The A1c test, also called the glycosylated hemoglobin test, is a blood test doctors use to determine how your blood sugar has been averaging over the past two to hree months. Your doctor may order this test if he or she suspects that you may be developing type 2 diabetes, or to see how well your blood sugar in controlled if you have diabetes.

Higher A1c levels are associated with higher blood sugar levels, which can lead to complications. A1c tests are done twice yearly for those with well controlled diabetes and four times a year if your A1c if higher than desired.

There is no need to prepare for the test. A medical professional will insert a needle in one of your veins, usually in an arm. They will collect a small amount of blood in a glass tube. Any discomfort will be temporary.

The A1c Test and Diabetes

After you eat, carbohydrates from food are broken down into blood sugar, called glucose. Glucose is a simple sugar that passes through the intestines into the bloodstream. As blood sugar levels rise after a meal, the pancreas releases insulin. Insulin is a hormone that allows glucose to pass from the blood into the cells. Cells then “burn” glucose for most of the energy they need.

Diabetes is a condition in which your body either does not make any or enough insulin and/or does not use the insulin the right way. When this happens, glucose levels in the bloodstream are high. High blood sugar can damage blood vessels and small nerves, so it’s important to keep blood sugar levels within a certain range.

Because the A1c test shows you how your blood sugar has been averaging over the last two to three months (called estimated average glucose), it can give a good picture of overall blood sugar control, and is used to help determine your risk for developing complications.

What Does the A1c Test Show?

The A1c test measures how much sugar is attached to hemoglobin. Hemoglobin is a protein found in red blood cells that helps carry oxygen throughout the body. Glucose attaches to protein in the blood naturally. When blood sugar is higher, more sugar is attached to hemoglobin. Since hemoglobin turns over every two to three months, the A1c test gives an idea of your average blood glucose over a two to three month period.

A healthy A1c level is less than 5.7 percent. According to the American Diabetes Association (ADA), a diagnosis can be made with the following values: a person may be diagnosed with diabetes if his or her HbA1c is greater than 6.5 percent.

  • Normal: A1c levels Less than 5.7 percent
  • Pre-diabetes: 5.7 to 6.4 percent
  • Diabetes: 6.5 percent or higher

For people with diabetes, recommended A1c values are as follows to lower risk of complications:

  • The American Diabetes Association recommends A1c values be under 7%*
  • The American Association of Endocrinologists recommend A1c values under 6.5%*

*Recommendations are individualized depending on your history. Be sure to talk to your health care team to find out your A1c goals.

If your A1c is above six percent, it may mean that you are pre-diabetic. Pre-diabetes is a condition that can occur before a person is formally diagnosed with type 2 diabetes, but can be reversed through improved diet and exercise.

A high A1c reading may also mean that you’re already diabetic, and you’re not controlling your blood sugar levels as well as you should. The longer a person’s A1c levels remain elevated, the greater the risk of developing side effects related to diabetes.

Higher A1c levels have been linked to higher risk of:

  • stroke and heart attack (cardiovascular disease)
  • kidney disease (nephropathy)
  • nerve damage (neuropathy)
  • eye damage that may result in blindness (retinopathy)

If your A1c value is high, your doctor and health care team will help you to change your treatment plan.

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Article Sources:

  • Bennett CM, Guo M, Dharmage SC. HbA(1c) as a screening tool for detection of Type 2 diabetes: a systematic review. 2007 Diabetes Med Apr;24(4):333-43. Epub 2007 Mar 15.  
  • Checking Your Blood Glucose - American Diabetes Association. (n.d.). American Diabetes Association Home Page - American Diabetes Association. Retrieved June 12, 2012, from http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/checking-your-blood-glucose.html
  • Lyons TJ, Basu A. Biomarkers in diabetes: hemoglobin A1c, vascular and tissue markers. 2012 Transl Res. Apr;159(4):303-12. Epub 2012 Jan 31.
  • Martins RA, Jones JG, et al. Glycated hemoglobin and associated risk factors in older adults. 2012 Cardiovasc Diabetol. Feb 6;11:13.
  • Mostafa SA, Davies MJ, et al. The potential impact of using glycated hemoglobin as the preferred diagnostic tool for detecting Type 2 diabetes mellitus. 2010 Diabet Med. Jul;27(7):762-9.
  • Paquot N, Scheen AJ. [Which HbA1c and lipid targets in patients with type 2 diabetes?]. 2012 Rev Med Liege. Feb;67(2):98-103.
  • Rubin J, Matsushita K, et al. Chronic hyperglycemia and subclinical myocardial injury. 2012 J Am Coll Cardiol. Jan 31;59(5):484-9.
  • Sartore G, Chilelli NC, et al. The importance of HbA1c and glucose variability in patients with type 1 and type 2 diabetes: outcome of continuous glucose monitoring (CGM). 2012 Acta Diabetol. Apr 1. [Epub ahead of print]
  • The A1C Test and Diabetes. (n.d.). National Diabetes Information Clearinghouse Home. Retrieved June 12, 2012, from http://diabetes.niddk.nih.gov/dm/pubs/A1CTest/
  • Zhuo X, Zhang P, et al. Alternative HbA1c cutoffs to identify high-risk adults for diabetes prevention: a cost-effectiveness perspective. 2012 Am J Prev Med Apr;42(4):374-81.
  • American Association of Clinical Endocrinologists. (2011). Medical Guidelines for Clinical Practice Developing a Diabetes Mellitus Comprehensive Care Plan. Retrieved from https://www.aace.com/files/dm-guidelines-ccp.pdf
  • American Diabetes Association. (January 2014). Standards of Medical Care in Diabetes—2014. Diabetes Care, 37(supplement 1), S14-S80. Retrieved from http://care.diabetesjournals.org/content/37/Supplement_1/S14.full#T6

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