What Is the A1C Test?

What to expect when undergoing this test

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The A1C test, also known as an HbA1C, hemoglobin A1C, glycated hemoglobin, or glycosylated hemoglobin test, is a blood test used to diagnose and monitor diabetes. It shows your average blood sugar levels for the past two to three months. This is a broader test than conventional home glucose monitoring, which measures your blood sugar at any given moment.

How the A1C test works
Illustration by Emily Roberts, Verywell

Purpose of Test

Hemoglobin A, a protein found inside red blood cells, carries oxygen throughout your body. When there's glucose in your bloodstream, it can stick (glycate) to hemoglobin A. The more glucose that's in your blood, the more it does this, creating a higher percentage of glycated hemoglobin proteins.

Lack of insulin or insulin resistance causes higher than normal levels of glucose in the blood.

Once glucose sticks to a hemoglobin protein, it typically remains there for the lifespan of the hemoglobin A protein (as long as 120 days). This means that, at any moment, the glucose attached to the hemoglobin A protein reflects the level of your blood sugar over the last two to three months.

The A1C test measures how much glucose is actually stuck to hemoglobin A, or more specifically, what percentage of hemoglobin proteins are glycated. Hemoglobin with glucose attached to it is called A1C. Thus, having a 7% A1C means that 7% of your hemoglobin proteins are glycated.

Depending on why your healthcare provider is ordering the test, the blood sample may be obtained from either a regular blood draw or by pricking your finger with a lancet.

Your healthcare provider may order an A1C test for the following reasons.

Screening for Diabetes

If you're overweight or obese and you have one or more other risk factors for developing type 2 diabetes, your healthcare provider will likely order an A1C test as part of your annual medical exam.

Such risk factors include:

The majority of people who end up with type 2 diabetes have prediabetes first, which means that their blood sugar is higher than normal, but not high enough to be diagnosed with diabetes. The A1C test can help monitor for this condition.

The American Diabetes Association (ADA) also recommends that everyone age 45 and older have the A1C test, regardless of other risk factors, because age itself is a major risk factor. If your test results are normal, you should have the A1C at least every three years.

If you were diagnosed with gestational diabetes (diabetes while pregnant) that resolved after you had your baby, you will need to be tested at least every three years for the rest of your life as well.

The A1C test can be used to screen high-risk pregnant women for undiagnosed pre-existing diabetes too, but only in the first trimester. During the second and third trimesters, diabetes needs to be screened with a glucose challenge test (also known as an oral glucose tolerance test) instead.

Diagnosing Diabetes

If you have symptoms like needing to urinate more often, feeling excessively thirsty and drinking more than normal, an increase in appetite, fatigue, cuts or bruises that heal slowly, and/or blurry vision, your healthcare provider may order an A1C test to check you for diabetes. Other symptoms may include weight loss or pain, tingling, or numbness in your hands or feet.

Your healthcare provider may also order a random plasma glucose test at the same time if you have these symptoms. This test measures your blood sugar level when your blood is taken.

If symptoms come on suddenly and your healthcare provider suspects acute-onset type 1 diabetes, you may be given a plasma blood glucose test instead of the A1C for diagnosis. However, some healthcare providers may do an A1C test as well to see how long blood sugar has been high.

Monitoring Diabetes

If you've been diagnosed with type 1 or type 2 diabetes, you'll periodically have an A1C test or other glycemic tests to monitor how well your disease is controlled and how your treatment is working.

How often you'll be tested will depend on what type of diabetes you have, how controlled it is, and what your healthcare provider recommends, but it will likely be at least twice a year.

Limitations

There are conditions in which the A1C test is not a reliable source for diagnosing diabetes, including:

These conditions can cause skewed results that don't reflect the reality of your blood sugar level. If you have one of these conditions, a fasting plasma glucose test and oral glucose tolerance test may be used for diagnosis instead.

Additionally, the A1C test needs to be done using methods that are certified by the NGSP and standardized to the Diabetes Control and Complications Trial (DCCT) analysis requirements in order to be as accurate as possible.

Before the Test

Once your healthcare provider recommends the A1C test, they'll let you know if they're going to do a random plasma glucose test at the same time. If you have questions about what your healthcare provider is looking for or what's going to happen, this is the time to ask.

Timing

The blood test typically takes less than five minutes once the technician is ready to draw your blood.

Location

You may have this blood test right in your healthcare provider's office or at a local hospital or lab.

What to Wear

It's helpful to wear short sleeves in case the technician draws blood from a vein in your arm. You can also just push or roll up a long sleeve instead.

Food and Drink

There are no fasting requirements for this test. The same goes for the random plasma glucose test.

Cost and Health Insurance

The A1C test is fairly inexpensive. If you have health insurance, it should be covered as other lab tests are whether it's done to screen for, diagnose, or monitor diabetes. You may have to pay a co-pay or co-insurance. Contact your health insurance company if you have any questions or concerns.

What to Bring

You can bring something to pass the time in the event you end up waiting for a while to get your blood drawn. Have your insurance and identification cards handy.

Other Considerations

You may have heard of A1C tests you can do at home. While these can be helpful in managing your disease once you're diagnosed with diabetes, they are not recommended for screening or diagnosing it. Talk to your healthcare provider about this if you have questions.

During the Test

A lab technician, often a nurse or a phlebotomist (a person who is specially trained to draw blood), will collect your blood sample for the test.

Pre-Test

You may need to fill out a form or two before the test, for example, to give consent for the test to be done or to authorize billing your insurance. The receptionist or nurse will let you know.

Be sure to let the technician know if you have a history of feeling faint or actually fainting during medical procedures. This allows the technician to take precautions, such as having you lie down on a table as your test is performed.

Throughout the Test

If your healthcare provider is screening for or trying to rule out or diagnose diabetes, you will have your blood drawn from a vein in your arm and sent to a lab that uses the NGSP-certified method.

The test will proceed as follows:

  • The technician will ask you which arm you want to use (most people choose their non-dominant arm). You'll roll up your sleeves, if applicable, to expose the area for the blood draw.
  • The technician will look for a vein—usually on the inside of your arm, in the crook of your elbow—and tie an elastic band around your arm above the vein to help push the blood down.
  • After the area is cleaned with alcohol, a small, fine needle will be inserted into your vein. You will probably feel a sharp prick, pinch, or poke that lasts for just a few moments. Let the technician know if you start to feel faint, dizzy, or lightheaded.
  • Your blood will be collected in a tube. As it begins to fill up, the technician will untie the elastic band and then take the needle out of your arm.
  • If the area is bleeding, a cotton ball or tissue will be pressed over it for a few seconds. If this doesn't stop the bleeding, the technician will place a bandage over the area.

If you're having an A1C test to monitor your diabetes after you've already been diagnosed, you'll probably have your finger pricked instead of the blood draw.

The results will be determined right there at your healthcare provider's office or lab. This is called a point-of-care test. It's a quick process that's mildly uncomfortable, but usually not painful, and one you will more than likely be used to at this point from testing your blood sugar levels at home.

Post-Test

As long as you aren't feeling nauseous or faint, you will be free to leave as soon as your blood sample has been taken. If you aren't feeling well, you may need to stay for a few minutes to recover first. As soon as you are up to it, you can leave.

After the Test

Once your test is complete, you can go home and resume your normal activities.

Managing Side Effects

You may have some bruising, pain, or bleeding at the site of the blood draw, but this should be mild and only last for a few days. If it lasts longer or gets worse, call your healthcare provider.

Interpreting Results

Depending on if your test was run in your healthcare provider's office or sent off to a lab, your results may be ready the same day, in a few days, or up to a week later.

For Diabetes Screening and Diagnosis

The reference ranges for A1C results are:

  • No diabetes: below 5.7%
  • Borderline/prediabetes: 5.7% to 6.4%
  • Diabetes: 6.5% or higher

For Monitoring Diabetes Control

Experts disagree somewhat on what the A1C target should be. The ADA recommends a general A1C target of less than 7% without significant hypoglycemia (low blood sugar), while the American Association of Clinical Endocrinologists (AACE) recommends a general target level of 6.5% or below.

The ADA's Standards of Medical Care in Diabetes for 2021 note the following A1C targets:

A1C Targets for Diabetes Management
Person Ideal A1C
Most non-pregnant adults without significant hypoglycemia <7%
Adults who take no medication or only oral medication; have a long life expectancy; or have no significant cardiovascular disease Target may be set lower than <7%
Adults with limited life expectancy or advanced micro- or macro-vascular disease <8%

The ADA recommends that an A1C target should only be set below 7% if it can be achieved without significant hypoglycemia or other adverse effects.

While helpful, these targets are general guidelines. Both the ADA and the AACE emphasize that A1C goals should be individualized based on factors such as:

  • Age
  • Other medical conditions
  • Length of time you've had diabetes
  • How well you comply with your treatment plan
  • Your risk of developing complications from hypoglycemia

For example, if you have a reduced life expectancy; you've had diabetes for a long time and difficulty attaining a lower A1C goal; you have severe hypoglycemia; or you have advanced diabetes complications such as chronic kidney disease, nerve problems, or cardiovascular disease, your A1C target goal might be higher than 7%, but typically no higher than 8%.

However, for most people, a lower A1C is ideal so long as they're not having frequent bouts of low blood sugar. Some people are able to substantially lessen their risk of complications from diabetes if they can keep their A1C under 7%.

In general, the higher your A1C, the higher your risk of developing complications from diabetes. Be open and honest with your healthcare provider about factors that can affect your A1C. They will determine what goal is best for you.

Estimated Average Glucose

Some labs report your estimated average glucose (eAG). This is your two- to three-month average glucose level reflected in mg/dL (milligrams per deciliter).

This is not the same as your A1C result, though that number is used to calculate eAG:

28.7 X A1C - 46.7 = eAG

Your A1c percentage can be translated into an estimated average blood sugar and vice versa.

For example, an average blood glucose of 150 mg/dL translates into an A1C of about 7%. This is above normal, given that a diagnosis of diabetes is usually given when blood sugar levels reach about 126 mg/dL.

The eAG is designed to help you relate your A1C to your home glucose monitoring, though it won't be the same as your daily levels since it reflects an average over a few months.

A1C to eAg Conversion Chart
HbA1c or A1C (%) eAg (mg/dL) eAg (mmol/L)
6 126 7.0
6.5 140 7.8
7 154 8.6
7.5 169 9.4
8 183 10.1
8.5 197 10.9
9 212 11.8
9.5 226 12.6
10 240 13.4

Skewed Results

Most people have one type of hemoglobin: hemoglobin A.

However, some people of African, Mediterranean, South or Central American, Caribbean, or Southeast Asian heritage, or people who have family members with sickle cell anemia or a sickle cell trait, have hemoglobin A and what's called a hemoglobin variant—a different type of hemoglobin.

Having a hemoglobin variant can affect the A1C test, making your blood sugar seem higher or lower than it actually is.

Sometimes this hemoglobin variant becomes obvious when your blood glucose test or your home monitoring glucose tests don't match your A1C results, when your A1C result is extremely high, or if a recent A1C test is very different from the previous one.

If your healthcare provider suspects that you have a hemoglobin variant based on your A1C results, they will likely order a blood test to confirm it. You can also ask for this test if you are concerned about this.

Follow-Up

What happens next will depend on why you had the A1C test, as well as your results.

Talk to your healthcare provider about any questions or concerns you have about your A1C test result and what your next steps are.

High A1C, No Symptoms of High Blood Sugar

If your A1C was high but you don't really have symptoms of high blood sugar, you may have another A1C test done.

Alternatively, your healthcare provider may decide to do a fasting plasma glucose test (FPG) or a two-hour glucose tolerance test right away instead.

In order to confirm the diagnosis of diabetes without the obvious symptoms of high blood sugar, two test results have to be abnormal. That could be two results of the same test (A1C, FPG, or two-hour tolerance test), or one result of one and one result of another.

High A1C With Symptoms of High Blood Sugar

If you do have symptoms of high blood sugar and your initial A1C is high, this will confirm a diabetes diagnosis—especially if you also had the random plasma glucose test done and that was high.

This means that your healthcare provider will need to see you as soon as possible to discuss starting a treatment plan to manage your diabetes.

This plan will depend on whether you have type 1 or type 2 diabetes, but may involve insulin supplementation, medication, glucose monitoring, exercise, and lifestyle changes.

Your healthcare provider will likely repeat the A1C soon after you've started treatment to see how it's working and how well you're complying.

Borderline/Prediabetes

If your A1C, FPG, or two-hour tolerance test results are borderline, your healthcare provider will repeat them at least every six months, as recommended by the ADA, to monitor your condition.

They will likely also talk to you about lifestyle changes you can make that can help prevent diabetes.

Normal Screening

If your healthcare provider was screening you for diabetes because you have risk factors and your A1C was normal, you will need this test at least every three years.

You may have it more often, depending on the initial results and your other risk factors. Your healthcare provider will discuss how often you need this test with you.

Monitoring

In cases where you're having your A1C tested to monitor your diabetes and your result is within your target range, you may only need to have the test repeated twice a year.

If it's higher than your target, your treatment plan may need some adjusting and your healthcare provider will likely repeat the test sooner.

The ADA recommends checking glycemic status through A1C or other glycemic tests at least twice a year for people whose diabetes is under control. But this may be done quarterly if you're newly diagnosed, your treatment plan has changed, or your diabetes isn't well-controlled.

Other Considerations

If a hemoglobin variant is confirmed, you can still have A1C tests done to monitor diabetes going forward, but they will need to be sent to a lab that uses a test that doesn't show interference from such variants.

Type 2 Diabetes Doctor Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Man

A Word From Verywell

If you do end up with a diabetes diagnosis, keep in mind that treatments are better than ever and, with careful attention to your treatment plan and following your healthcare provider's instructions to the letter, you can live your best life.

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10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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