Every three to six months, your internist or
general practitioner may request a blood sugar test called a hemoglobin A1C
test—also known as the HbA1C, glycohemoglobin, glycosylated hemoglobin, or
glycated hemoglobin test. This test shows how well you have been managing your
blood sugar for the six to 12-week period prior to your test.
You will still continue your at-home blood
sugar testing, but this will help show your doctor if your plan is effective,
or if you all need to rework your diabetes management.
What is Hemoglobin?
Hemoglobin is a substance within your red
blood cells that carries oxygen through your body. If your diabetes is not
controlled well, excess sugar will build up on the hemoglobin over time. Coated
hemoglobin is called “glycated.” An A1C test measures how much glycated hemoglobin
is in your blood. The more glycated hemoglobin present in your blood, the more
out of control your diabetes has been in recent weeks, and the poorer your
control. The higher the A1C level, the higher your risk of developing
complications from diabetes.
Why Have an A1C Test?
Your doctor will use an A1C test to make an
initial diabetes diagnosis—this establishes a baseline A1C level for the future—and
he will use it to monitor your diabetes and see how your treatment plan is
For those who have had diabetes for several
years, consider an A1C test a maintenance test—to make sure you don’t require a
change to your plan. The A1C test gives
you a months-long reading of your blood sugar level.
How often should I be tested?
This depends on the type of diabetes you
have, your treatment plan, and how well you’ve previously managed your blood
- If you have type 1 diabetes, you will likely be tested more frequently—as much
as four or more times a year.
- If you have type 2 diabetes, don’t use insulin, and have a history of keeping your
blood sugar level within the healthy range, your doctor may only
ask to test your blood twice a year.
- If you have type 2 diabetes, use insulin, and have had trouble in the past with
keeping your blood sugar within the healthy target range, your doctor may
ask to test your hemoglobin four or more times a year.
What results should you expect?
For people who don’t have diabetes, the
upper limit of normal for HbA1c is 5.6 percent. The goal for people with
diabetes is individualized, with the gial determined between patient and healthcare provider. In general, the higher the A1C,
the greater the risks of developing complications related to diabetes.
If you are taking the A1C test to diagnose
diabetes, two consecutive A1C readings
over 6.5 percent are an indication of diabetes. An A1C reading between 5.7
and 6.4 percent is indicative of prediabetes—this means you are at risk for
developing diabetes if you do not take steps to prevent it.
When an A1C test won’t work
The effectiveness of an A1C test may be
limited in certain cases. Here are a few:
- If you are anemic or have low
levels of iron in your blood, your A1C test may return falsely high
- If you experience heavy or
chronic bleeding (possibly from your menstrual cycle), you may have an
unusually low amount of hemoglobin. This will likely return a falsely low
percentage for your A1C test.
- If your hemoglobin has a
variant—meaning you have an uncommon form of hemoglobin—your A1C test may be
false. A hemoglobin variant can be confirmed by a lab test, but your future A1C
tests will need to be read by a specialized lab that is equipped to test your
particular hemoglobin variant.