By Adam Garcia
This week in Diabetic Dictionary we will find out what an HbA1c is. The HbA1C is also known as the Hemoglobin A1c, Glycohemoglobin, Glycated hemoglobin, and Glycosylated hemoglobin. The formal name is A1c and estimated Average Glucose (eAG). Let’s see what it is all about.
How is it used?
The HbA1c test is used primarily to monitor the glucose control of diabetics over time. The goal of those with diabetes is to keep their blood glucose levels as close to normal as possible. This helps to minimize the complications of elevated glucose levels, such as progressive damage to body organs like the kidneys, eyes, cardiovascular system, and nerves. The HbA1c test result give a picture of the average amount of glucose in the blood over the last few months. They can help you and your doctor know if the measures you are taking to control your diabetes are successful or need to be adjusted.
This test is frequently used to help newly diagnosed diabetics determine how elevated their uncontrolled blood glucose levels have been. It may be ordered several times while control is being achieved, and then several times a year to verify that good control is being maintained.
When is it ordered?
Depending on the type of diabetes that you have, how well your diabetes is controlled, and your doctor, your HbA1c may be measured 2 to 4 times each year. The American Diabetes Association recommends testing yourself at least twice a year. When someone is first diagnosed with diabetes or if control is not good, the HbA1c may be ordered more frequently.
What does the test result mean?
The HbA1c is currently reported as a percentage, and it is recommended that diabetics aim to keep their HbA1c level below 7%. The report for your HbA1c test also may include an estimated Average Glucose (eAG), which is a calculated result, based on your HbA1c levels. The purpose of reporting eAG is to help you relate your HbA1c results to your everyday glucose monitoring levels. The formula for eAG converts percentage HbA1c to units of mg/dL or mmol/L so that you can compare it to your glucose levels from home monitoring systems or laboratory tests.
It should be noted that the eAG is still an evaluation of your glucose over the last couple of months. It will not match up exactly to any one daily glucose test result. The American Diabetes Association has adopted this calculation and provides a calculator and information on the eAG on their web site.
A non-diabetic person will have an HbA1c between 4% and 6%. The closer a diabetic can keep their HbA1c to 6% without experiencing excessive hypoglycemia, the better their diabetes is in control. As the HbA1c and eAG increase, so does the risk of complications.
Is there anything else I should know?
The HbA1c test will not reflect temporary, acute blood glucose increases or decreases. The glucose swings of someone who has “brittle” diabetes will not be reflected in the HbA1c.
If you have a hemoglobin variant, such as sickle cell hemoglobin (hemoglobin S), you will have a decreased amount of hemoglobin A. This may limit the usefulness of the HbA1c test in monitoring your diabetes. If you have anemia, hemolysis, or heavy bleeding, your test results may be falsely low. If you are iron deficient, you may have an increased HbA1c measurement. If you have had a recent transfusion, then your HbA1c will be falsely increased (blood preservative solutions contain high glucose levels) and not accurately reflect your glucose control for 2 to 3 months.
Some Common Questions
1. How is estimated Average Glucose (eAG) calculated?
The ADAG formula that is used to calculate the eAG from your HbA1c result is:
28.7 X HbA1c – 46.7 = eAG
An example of this is an HbA1c of 6%. The calculation for this would be:
28.7 X 6 – 46.7 = 126 mg/dl
for an estimated average glucose of 126 mg/dl.
What this means is that for every one percent that your HbA1c goes up, it is equivalent to your average glucose going up by about 29 mg/dl.
2. Is there a home test for HbA1c?
Yes. There are FDA-approved tests that can be used at home. If you are interested in learning more, visit the article on Home Tests and ask your doctor.
3 Can the HbA1c test be used to screen for or diagnose diabetes?
This is a question that is currently being explored by the medical community, but the HbA1c test is not yet recommended for these purposes. The HbA1c test has the advantages of not requiring a person to be fasting and of giving an estimate of glucose levels for the past couple of months. There are, however, conditions such as anemia or the presence of hemoglobin variants that can interfere with the test’s interpretation. And there are currently no established cutoff values to compare HbA1c test results to in order to use them for diabetes screening or diagnosis.
4. Are all HbA1c tests the same?
Not yet, but great strides have been made in standardizing the HbA1c test.
For more questions on this topic or if you wish to make a comment please email us or leave a reply below.
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My grandparents both have diabetes, and it kind of a scary thing. Luckily we are able to do things about it now. If this were a hundred years ago, things would be a lot different.