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HbA1c

Definition

HbA1c is a lab test that shows the average level of blood sugar (glucose) over the previous 3 months. It shows how well you are controlling your diabetes. 

Alternative Names

Glycated hemoglobin; Glycosylated hemoglobin; Hemoglobin - glycosylated; A1C; GHb; Glycohemoglobin

How the test is performed

A blood sample is needed. Some methods only require a quick finger stick. Others may need a sample of blood from a vein.

How to prepare for the test

No special preparation is needed.

How the test will feel

When the needle is inserted, you may feel a slight pinch or some stinging. Afterward, there may be some throbbing.

Why the test is performed

Your doctor may order this test if you have diabetes. It shows how well you are controlling your diabetes.

The test may also be used to screen for diabetes.

Normal Values

An HbA1c of 5.6% or less is normal.

The following are the results when the HbA1c is being used to diagnose diabetes:

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

If you have diabetes, you and your doctor or nurse will discuss the correct range for you. For many people the goal is to keep your level at or below 6.5 - 7%.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results. The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

What abnormal results mean

Abnormal results mean that you have had high blood sugar levels over a period of weeks to months.

If your HbA1c is above 6.5% and you do not already have diabetes, you may be diagnosed with diabetes.

If your level is above 7% and you have diabetes, it often means that your is not well controlled. Your target HbA1c should be determined by you and your health care provider.  

In general, the higher your HbA1c, the higher the risk that you will develop problems such as:

If your HbA1c stays high for a long period of time, the risk for these problems is even greater.

Ask your doctor how often you should have your level tested. Usually, doctors recommend testing every 3 or 6 months.

What the risks are

Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

References

American Diabetes Association. Standards of medical care in diabetes--2012. Diabetes Care. 2011 Jan;35 Suppl 1:S11-63.

Buse JB, Polonsky KS, Burant CF. Type 2 diabetes mellitus. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 31.

Inzucchi SE, Sherwin RS. Type 2 diabetes. In: Goldman L,Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier;2011:chap 237.


Review Date: 4/29/2012
Reviewed By: Shehzad Topiwala, MD, Chief Consultant Endocrinologist, Premier Medical Associates, The Villages, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine, and David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
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