What Is an A1C Test?
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What Is the A1C Test for Diabetes?

What Is the A1C Test for Diabetes?
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What Is the A1C Test

Learn about the importance of the A1C test in diagnosing and managing diabetes and prediabetes.
What Is the A1C Test

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An A1C test, also known as a hemoglobin A1C or HbA1C test, is a simple blood test that estimates your average blood sugar levels over the last three months.

People who don’t have diabetes may be given this test at a wellness visit to screen for prediabetes or diabetes. People who have diabetes may use an A1C test to monitor how well their disease is being managed.

Who Typically Needs an A1C Test?

A1C tests are performed routinely on people with and without diabetes.

People With Diabetes

If you already have diabetes, your initial diagnosis may have been given based on the results of an A1C test. Regular A1C tests are also one of the most important health markers for people with diabetes after a diagnosis.

Measuring A1C levels is perhaps the best tool your healthcare providers have for monitoring the progression of your diabetes and the success of your treatment. Your A1C measurement gives a clinician or diabetes educator a single snapshot of how high or low your blood sugar levels have been over the past several months. Your A1C results will help determine whether your diabetes management plan — including diet, exercise, medication, and other lifestyle changes — needs adjustment.

Most people with diabetes are advised to get new A1C checks every three to six months.

People Without Diabetes

An A1C test is also one of the most common and reliable ways of diagnosing prediabetes and diabetes:


A1C Test Results
Normal Blood Sugar
Below 5.7 percent
Prediabetes
5.7 to 6.4 percent
Diabetes
6.5 percent or above

If your A1C result is in the diabetic or prediabetic range, your clinician may choose to administer another test, such as a fasting blood glucose test or an oral glucose tolerance test, to confirm your diagnosis.

If you are experiencing some of the symptoms of high blood sugar — such as frequent urination, intense thirst, or blurry vision — your doctor may give you an A1C test to check for diabetes.

Others will receive an A1C test as a matter of routine during a checkup or wellness visit. And some healthcare professionals will choose to screen adults with certain risk factors for diabetes.

The U.S. Preventive Services Task Force recommends diabetes screening for all adults over the age of 35 who are overweight or who have obesity, and it suggests that doctors screen people at an even earlier age if they have one of the following additional risks:

How Is an A1C Test Performed?

An A1C test uses a simple blood sample and doesn’t require any special preparation.

During an office visit, a nurse or phlebotomist will take a blood sample from a vein or finger and send it to a lab to be analyzed.

An A1C test doesn’t require fasting. You can eat and drink normally prior to the test, unlike with a fasting glucose or cholesterol test, and the results will not be significantly affected if your blood sugar happens to be unusually high or low at the time of the test.

Blood tests pose very little risk. It’s possible that there may be some bruising or soreness in the area where the needle was inserted, but it typically goes away quickly. You may also want to avoid lifting heavy objects for 24 hours after the test.

It is also possible to purchase an at-home A1C test, although these products are probably less reliable than a test conducted by a certified laboratory.

What Do My A1C Results Mean?

A1C results are reported as a percentage in the United States. To find your average blood sugar level over the past several months, you can convert the number into the same measurement that your blood sugar meter or continuous glucose monitor uses:


A1C (Percentage)
Average Glucose Level (mg/dL)
5.0
97
6.0
126
7.0
154
8.0
183
9.0
212
10.0
240
11.0
269
12.0
298

Some lab reports will also list this second number, which may be labeled “estimated average blood glucose (eAG).”

In many other countries, A1C and blood sugar measurements are given in different units.

What’s Next?

Your A1C test results will help a clinician to determine the recent history of your blood sugar levels, which are an important aspect of your metabolic and overall health.

If you’ve never been diagnosed with prediabetes or diabetes, the results of your A1C test will help your healthcare provider determine whether you have either of those conditions, or it could indicate that you are at risk of developing them in the future. You may be asked to try to lose weight, change your diet or exercise habits, or take a new medication.

If you have already been diagnosed with diabetes, your A1C result will help determine how well your treatment has been working.

High A1C results, which indicate that your blood sugar has been chronically elevated above a healthy range, are strongly correlated with the complications of diabetes, including vision loss, nerve damage, kidney failure, and cardiovascular disease. People with diabetes who can keep their A1C below 7 percent, the target set for most nonpregnant adults by American health authorities, have a significantly reduced risk of diabetic complications.

If your A1C result is above the target set by your healthcare provider, you may be asked to increase your diabetes management efforts. This could include making new changes to your diet and exercise habits or to how frequently you check your blood sugar. You may also be prescribed new diabetes medications or larger doses of your existing medications.

The Takeaway

  • The A1C test measures average blood sugar levels over the past three months and is an essential part of diagnosing and managing diabetes.
  • An A1C test uses a standard blood draw, and it doesn’t require any special preparation or recovery.
  • It is recommended that most adults with diabetes keep their A1C below 7 percent; higher numbers are associated with a greater risk of diabetes complications.
  • Your healthcare provider should use your A1C results to make recommendations about the way you manage your diabetes or prediabetes, including changes to your medication or your diet, exercise, and lifestyle habits.

Common Questions & Answers

Why do I need an A1C test?
This blood test is essential for diagnosing prediabetes and diabetes. It also monitors the blood sugar levels of people who have already been diagnosed with those health conditions.
People will have different goal numbers depending on their general health and diabetes history. Some people with diabetes may be able to lower their risk of complications if they keep their A1C levels below 7 percent.
If you have diabetes, you should be tested at least twice a year. Your doctor may recommend more frequent testing if your blood sugar levels aren’t at the target number.
If your numbers are above the range that’s ideal for you, talk to your diabetes care team right away.
A1C tests are an average of glucose levels over the course of three months, so they aren’t a precise tool for gauging day-to-day blood sugar levels. Continuous glucose monitors are more effective for that.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. The A1C Test and Diabetes. National Institute of Diabetes and Digestive and Kidney Diseases. April 2018.
  2. What Is the A1C Test? American Diabetes Association.
  3. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes — 2024. Diabetes Care. December 11, 2023.
  4. Pippitt et al. Prediabetes and Type 2 Diabetes: Screening. U.S. Preventive Services Task Force. August 14, 2021.
  5. A1C. Cleveland Clinic. November 22, 2022.
  6. What You Need to Know About Blood Testing. MedlinePlus. August 15, 2024.
  7. Jacobsen LM et al. Accuracy of Three Commercial Home-Use Hemoglobin A1c Tests. Diabetes Technology & Therapeutics. November 2022.
  8. Convert Between NGSP, IFCC and eAG. National Glycohemoglobin Standardization Program.
  9. 6. Glycemic Goals and Hypoglycemia: Standards of Care in Diabetes — 2024. Diabetes Care. December 11, 2023.
  10. Boye KS et al. The Association Between Sustained HbA1c Control and Long-Term Complications Among Individuals with Type 2 Diabetes: A Retrospective Study. Advances in Therapy. March 22, 2022.
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Anna L. Goldman, MD

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Anna L. Goldman, MD, is a board-certified endocrinologist. She teaches first year medical students at Harvard Medical School and practices general endocrinology in Boston.

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