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Endocrine and Immune System Conditions

Blood Test: Hemoglobin A1c

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What It Is

A hemoglobin A1c (HbA1c) test is used to monitor long-term glucose (sugar) control in people with diabetes. While daily blood sugar testing gives a picture of day-to-day fluctuations, the hemoglobin A1c test offers an overview of how well glucose has been controlled over the past 2 to 3 months.

The test assesses the amount of glycated (sugar-coated) hemoglobin in the blood. Hemoglobin is the oxygen-carrying protein found in red blood cells. Protein and sugar naturally stick together, and there's more sugar in the blood of people with poorly controlled diabetes, so they tend to have a higher percentage of HbA1c in their blood.

Because the sugar stays attached to hemoglobin for the life of the red blood cell (about 120 days) doctors can use the test to determine the person's average blood sugar levels over that time.

Why It's Done

Doctors use the hemoglobin A1c test to determine if your child's diabetes management plan needs to be adjusted. Typically the test is performed in a clinical laboratory or the doctor's office and repeated a few times a year. The HbA1c test may be done more frequently if your child is newly diagnosed, has changed medications, or is starting a new treatment plan.

Close monitoring of HbA1c and blood sugar levels can help you and your doctor adjust your child's treatment plan to improve blood sugar control. This is very important for lowering your child's risk of developing potential long-term complications of diabetes, which can include heart disease, and stroke, as well as kidney, vision, and nerve problems.

Preparation

No special preparations are needed for this test. Having your child wear a short-sleeve shirt on the day of the test can make things faster and easier for the technician who will be drawing the blood.

The Procedure

A health professional will usually draw the blood from a vein. For an infant, the blood may be obtained by puncturing the heel with a small needle (lancet). If the blood is being drawn from a vein, the skin surface is cleaned with antiseptic, and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.

After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting the blood for the test will only take a few minutes.

drawing_blood

heel_prick_illustration

What to Expect

Either method (finger or heel sticking or vein withdrawal) of collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a few days.

Getting the Results

Many doctors, especially those who specialize in treating diabetes, have blood-analysis equipment in their office and will be able to analyze the results immediately. Other doctors may send blood samples to a lab for analysis.

Generally, as hemoglobin A1c levels increase, so does the risk of complications. However, it's important to know that since labs and offices may use different methods to measure HbA1c, the range of normal values for the test results may vary. Your doctor can help you interpret and compare the results if your child has had tests done by different labs.

Risks

The HbA1c test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn:

  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin causing a lump or bruise)
  • pain associated with multiple punctures to locate a vein

Helping Your Child

Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear.

Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and remain still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help if your child looks away when the needle is being inserted into the skin.

If You Have Questions

Although the hemoglobin A1c test is a useful tool, it isn't intended to replace daily glucose testing and shouldn't be used alone to adjust your child's insulin dosage.

If you have any questions about the hemoglobin A1c test, talk to your doctor.

Reviewed by: Steven Dowshen, MD
Date reviewed: February 2011

License

Note: All information is for educational purposes only. For specific medical advice, diagnoses and treatment, consult your doctor.

© 1995–2014 The Nemours Foundation/KidsHealth. All rights reserved.

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