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A1C Test for Diabetes

What is the A1C test?

The A1C ("A-one-C") is a blood test that can be use to check your average blood sugar control over the past 2 to 3 months. This average is different from your day to day blood sugar. There are 3 reasons to check your A1C:

  • to diagnose prediabetes
  • to diagnose diabetes
  • to check how well you are controlling your blood sugar

Sugar absorbed from your digestive system circulates in the bloodstream. The sugar attaches to the hemoglobin protein in red blood cells, forming hemoglobin A1C. The A1C stays in the blood for the life of the red blood cell, which is 90 to 120 days. This means that the amount of A1C in your blood reflects how high your blood sugar has been over the past 3 months.

Another name for this test is hemoglobin A1C test. It is different from a regular blood sugar or blood glucose test.

Why is this test done?

A1C is an excellent way to check how well you are controlling your blood sugar over a 3-month period.

A1C measurements are important because:

  • They can show that your daily home blood sugar results are accurate.
  • They help predict your risk of diabetic complications. The higher the A1C percentage, the greater your risk of serious problems from diabetes, like eye, kidney, blood vessel, or nerve damage.

If your A1C is high, your diabetes plan may need to be changed.

How do I prepare for this test?

No preparation is necessary. One of the advantages of this test is that you do not have to fast before you take it.

How is the test done?

A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab.

Having this test will take just a few minutes of your time.

At some pharmacies you may be able to buy a device that allows you to test A1C at home. You may find that the results of the home test are not the same as results of tests done at your provider's office.

How will I get the test result?

Ask your healthcare provider when and how you will get the result of your test.

What does the test result mean?

The A1C percentage rises as your average blood sugar level rises.

  • The normal range for a person without diabetes is 4 to 5.6%.
  • The range for prediabetes is 5.7 to 6.4%.
  • Diabetes is diagnosed if your A1C is 6.5% or higher.
  • The blood sugar goal for most adults with diabetes is an A1C below 7%.

Discuss what your A1C level should be with your healthcare provider.

The following chart shows examples of how the A1C is related to your average blood sugar (glucose) level:


  A1C      Estimated Average Glucose (eAG)
---------------------------------------------
  6%         126 mg/dL (7.0 mmol/L)
  7%         154 mg/dL (8.6 mmol/L)
  8%         183 mg/dL (10.2 mmol/L)
  9%         212 mg/dL (11.8 mmol/L)
 10%         240 mg/dL (13.3 mmol/L)
 11%         269 mg/dL (14.9 mmol/L)
 12%         298 mg/dL (16.6 mmol/L)
---------------------------------------------

Remember that, even though you have this test every few months, you need to keep testing your blood sugar at home as often as your provider recommends. The blood sugar test results help you and your healthcare provider know if you are on the best medicine dose and schedule for the daily ups and downs of your blood sugar.

Previously the hemoglobin A1C was reported only as the percentage. Now it is also available from most labs as the eAG, or estimated average glucose. If you know your A1C, you can use the chart above to know what your average blood glucose has been. Many healthcare providers will soon be reporting your results to you as both your A1C percentage and your average blood sugar.

What if my test result is not normal?

If you have not yet been diagnosed with diabetes and your test is not normal, you need to talk with your healthcare provider about whether you have diabetes.

If you have been diagnosed with diabetes and your test is not normal, your healthcare provider will talk to you about how to lower your blood sugar with medicine if you have type 1 diabetes, or with diet, exercise, and/or medicine if you have type 2 diabetes. Keeping your blood sugar levels and A1C levels in or near normal ranges will help you avoid the complications of diabetes, such as eye disease, kidney disease, or nerve damage.

If your test results are not normal, ask your healthcare provider:

  • if you need additional tests
  • what you can do to work toward a normal value
  • when you need to be tested again.

The A1C test should be done every 3 months unless you are in good control. If you do have good control of your blood sugar, your provider may recommend having the test every 6 months.

Developed by RelayHealth.
Published by RelayHealth.
Last modified: 2011-05-23
Last reviewed: 2011-03-03
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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