Glycohemoglobin Test

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Update Date 12/05/2020
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Know the basics

What is Glycohemoglobin Test?

A glycohemoglobin test, or hemoglobin A1c, is a blood test that checks the amount of sugar (glucose) bound to the hemoglobin in the red blood cells. When hemoglobin and glucose bond, a coat of sugar forms on the hemoglobin. That coat gets thicker when there’s more sugar in the blood. A1c tests measure how thick that coat has been over the past 3 months, which is how long a red blood cell lives. People who have diabetes or other conditions that increase their blood glucose levels have more glycohemoglobin (sugar bound to hemoglobin) than normal.

An A1c test can be used to diagnose prediabetes or diabetes. The A1c test checks the long-term control of blood glucose levels in people with diabetes. Most doctors think checking an A1c level is the best way to check how well a person is controlling his or her diabetes.

A home blood glucose test measures the level of blood glucose only at that moment. Blood glucose levels change during the day for many reasons, including medicine, diet, exercise, and the level of insulin in the blood.

It is useful for a person who has diabetes to have information about the long-term control of blood sugar levels. The A1c test result does not change with any recent changes in diet, exercise, or medicines.

Glucose binds to hemoglobin in red blood cells at a steady rate. Since red blood cells last 3 to 4 months, the A1c test shows how much glucose is in the plasma part of blood. This test shows how well your diabetes has been controlled in the last 2 to 3 months and whether your diabetes treatment plan needs to be changed.

The A1c test can also help your doctor see how big your risk is of developing problems from diabetes, such as kidney failure, vision problems, and leg or foot numbness. Keeping your A1c level in your target range can lower your chance for problems.

Why is Glycohemoglobin Test performed?

Depending on the type of diabetes that you have, how well their diabetes is controlled, and on doctor recommendations, the A1c test may be measured 2 to 4 times each year. When you are first diagnosed with diabetes or if control is not good, A1c may be ordered more frequently.

For diagnostic and screening purposes, A1c may be ordered as part of a health checkup or when you are suspected of having diabetes because of signs or symptoms of increased blood glucose levels (hyperglycemia) such as:

  • Increased thirst
  • Increased urination
  • Fatigue
  • Blurred vision
  • Slow-healing infections

Things to know before

What should I know before receiving Glycohemoglobin Test?

The A1c test will not reflect temporary, acute blood glucose increases or decreases, or good control that has been achieved in the last 3-4 weeks. The glucose swings of someone who has “brittle” diabetes will also not be reflected in the A1c.

If an individual has a hemoglobin variant, such as sickle cell hemoglobin (hemoglobin S), they will have a decreased amount of hemoglobin A. This may limit the usefulness of the A1c test in diagnosing and/or monitoring this person’s diabetes, depending on the method used.

If a person has anemia, hemolysis, or heavy bleeding, A1c test results may be falsely low. If someone is iron-deficient, the A1c level may be increased.

If a person has had a recent blood transfusion, the A1c may be inaccurate and may not accurately reflect glucose control for 2 to 3 months.

Know what happens

How to prepare for Glycohemoglobin Test?

You do not need to stop eating before you have an A1c test. This test can be done any time during the day, even after a meal.

What happens during Glycohemoglobin Test?

The health professional taking a sample of your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.

What happens after Glycohemoglobin Test?

An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

You may remove the tape and cotton in about 20 to 30 minutes. You will be dated to get the results of your test. Your doctor will explain what your test results mean for you. You should follow the instructions of your doctor.

Understand the results

What do my results mean?

The diagnosis of diabetes needs to be confirmed by repeating the same blood sugar test or doing a different test on another day.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Hemoglobin A1c
Normal Less than 5.7%
Prediabetes (increased risk for diabetes) 5.7%–6.4%
Diabetes 6.5% and higher

Most nonpregnant adults who have type 1 or type 2 diabetes should aim to have an A1c level less than 7%.

Most children with type 2 diabetes should aim to have an A1c level less than 7%.

You should talk to your doctor about your diabetes treatment plan and your target A1c goal.

A1c and estimated average glucose (eAG)
A1c % Estimated average plasma glucose Estimated average plasma glucose
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 13.4 mmol/L
11% 269 mg/dL 14.9 mmol/L
12% 298 mg/dL 16.5 mmol/L
A1c recommendations for children and teens with type 1 diabetes
Age A1c %
Children younger than 6 years old Less than 8.5%
Children ages 6–12 years old Less than 8%
Teens ages 13–19 years old Less than 7.5%

High values

Some medical conditions can increase A1c levels, but the results may still be within a normal range. These conditions include Cushing’s syndrome, pheochromocytoma, and polycystic ovary syndrome (PCOS).

Corticosteroid treatment increases the A1c level.

Depending on the laboratory and hospital, the normal range for Glycohemoglobin Test may vary. Please discuss with your doctor any questions you may have about your test results.

If you have any questions about the Glycohemoglobin Test, please consult with your doctor to better understand your instructions.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Read also:

    Sources

    Porter, R. S., Kaplan, J. L., Homeier, B. P., & Albert, R. K. (2009). The Merck manual home health handbook. Whitehouse Station, NJ, Merck Research Laboratories. Print edition. Page 828
    Guillain-Barré syndrome http://www.mayoclinic.org/diseases-conditions/guillain-barre-syndrome/basics/definition/con-20025832. Accessed July 15, 2016.
    Guillain-Barré syndrome https://www.nlm.nih.gov/medlineplus/ency/article/000684.htm. Accessed July 15, 2016.

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