Glycohemoglobin (HbA1c, A1c)
Glycohemoglobin (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 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.
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
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 It Is Done
This test is done to:
- Diagnose prediabetes and diabetes.
- Check your
treatment for diabetes.
How To Prepare
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.
How It Is Done
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
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is
- Put a gauze pad or cotton ball over the needle site as the needle
- Put pressure on the site and then put on a bandage.