HbA1c is a blood test doctors use to determine how high your blood sugar has been in the past few months. Your doctor may order this test if ...

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HbA1c is a blood test doctors use to determine how high your blood sugar has been in the past few months. Your doctor may order this test if you are diabetic or if he or she suspects that you may be developing type 2 diabetes. People undergoing treatment for diabetes usually have the HbA1c test at least twice a year.

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.

If you’re already being treated for diabetes, this simple test can show if you’re maintaining steady blood sugar levels. Diabetic patients usually take at least one drug to help control their blood sugar levels, while some patients take more. Others may need to take insulin. People with high blood sugar have hyperglycemia.

The HbA1c Test and Diabetes

After you eat, starches from food are broken down into 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 helps guide glucose molecules into the body’s cells. Cells then “burn” glucose for most of the energy they need.

Diabetes is a condition in which your body has trouble effectively converting glucose (sugar) to energy. When this happens, glucose levels in the bloodstream spike. High blood sugar can damage blood vessels and small nerves, so it’s important to keep blood sugar levels within a certain range.

When you fast (go without any food) for 12 hours, your blood sugar should be less than 100 mg/dL. If it isn’t, you may be hyperglycemic. Your doctor may order an HbA1c test to get a “snapshot” of your average blood glucose levels over the previous few months.

What Does the HbA1c Test Show?

Hemoglobin is a protein found in red blood cells that helps carry oxygen throughout the body. HbA1c forms when hemoglobin reacts with glucose in the bloodstream. HbA1c is a biomarker, or biological substance, which reflects health or disease in the body.

Glycated hemoglobin builds up in a predicable fashion. If you are healthy and producing enough insulin, your blood glucose levels remain within a steady range throughout the day. A healthy body produces enough insulin, and the body’s cells react to insulin as they should.

A healthy HbA1c level is less than six percent. According to the American Diabetes Association (ADA), a person may be diagnosed with diabetes if his or her HbA1c is greater than 6.5 percent. Different laboratories may use different ranges. However, the following is a general guideline for HbA1c ranges, as noted by the National Diabetes Information Clearinghouse (NDIC):

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

If your HbA1c 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 HbA1c reading may also mean that you’re already diabetic, and you’re not controlling your blood sugar levels as well as you should. Diabetes patients should attempt to keep their HbA1c levels at seven percent or below. The longer a person’s HbA1c levels remain elevated, the greater the risk of developing side effects related to diabetes.

If your blood sugar has been high, your doctor may prescribe a higher dose of the drug you are taking to control your condition. He or she may also try new medications, or you may begin taking insulin, if you’re not already.

Higher HbA1c levels have been linked to many undesirable conditions, including:

  • higher risk of stroke and heart attack (cardiovascular disease)
  • kidney disease (nephropathy)
  • nerve damage (neuropathy)
  • eye damage that may result in blindness (retinopathy)
Written by: Dale Kiefer
Edited by:
Medically Reviewed by: George Krucik, MD
Published: Jul 25, 2012
Last Updated: Oct 8, 2013
Published By: Healthline Networks, Inc.
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  • 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.
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