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The A1C Test

What is the A1C test?

The A1C test, also called the glycosylated hemoglobin test, is a blood test doctors use to determine your average blood sugar levels over the past three months. Your doctor may order this test if they suspect that you have or are developing type 2 diabetes. Alternately, if you have diabetes, they may order this test to determine if current treatment is keeping your blood sugar under control.

Higher A1C levels are associated with higher blood sugar levels, which can lead to medical complications. A1C tests can be done at different times for different patients. They are usually done two or three times per year for people with well-controlled diabetes. Doctors may order additional tests if your A1C levels are higher than desired.

There is no need to prepare for the test. A medical professional will insert a needle in one of your veins, usually in an arm. They will collect a small amount of blood in a glass tube. There may be some discomfort associated with a needle entering the skin to get to the vein for blood collection. However, any discomfort will be temporary.

The A1C test and diabetes

After you eat, carbohydrates from food are broken down into different components including sugar, called glucose. Glucose is a simple sugar that passes through the intestines into the bloodstream. As blood sugar levels rise after a meal, the pancreas releases insulin. Insulin is a hormone that allows glucose to pass from the blood into the cells. Cells then use glucose for the energy they need to grow and serve other functions in the body.

Diabetes is a condition in which your body does not make any or enough insulin or does not use the insulin the right way. When this happens, glucose levels in the bloodstream become elevated, since the glucose cannot enter the cells to be used as energy. High blood sugar can damage blood vessels and small nerves, so it’s important to keep blood sugar levels within a certain range.

The A1C test shows your average blood sugar levels over the last three months (called estimated average glucose). It can give a good picture of overall blood sugar control. It is used to help determine your risk for developing complications.

Understanding the results of the A1C test

The A1C test measures how much sugar is attached to hemoglobin. Hemoglobin is a protein found in red blood cells. It helps carry oxygen throughout the body. Glucose naturally attaches to the protein on the outside of the red blood cell circulating in the blood. When blood sugar is higher, more sugar is attached to hemoglobin. Since hemoglobin turns over every three months, the A1C test gives an idea of your average blood glucose levels over a three-month period.

A healthy A1C level is less than 5.7 percent. According to the National Institute of Diabetes and Digestive and Kidney Diseases, a diagnosis can be made with the following values:

  • Normal: A1C levels lower than 5.7 percent
  • Prediabetes: 5.7 to 6.4 percent
  • Diabetes: 6.5 percent or higher

For people with diabetes, the recommended A1C values are as follows to lower risk of complications:

  • The American Diabetes Association recommends A1C values of lower than 7 percent.
  • The American Association of Endocrinologists recommends A1C values of lower than 6.5 percent.

Keep in mind that recommendations are individualized. Your goal A1C level will be based on your health history and other medical conditions that may be affecting your health. Be sure to talk to your healthcare team to learn your A1C goals.

If your A1C is above 5.7 percent, it may mean that you have prediabetes. Prediabetes is a condition that can occur before a person is formally diagnosed with type 2 diabetes. It can usually be reversed through improved diet and exercise.

A high A1C reading may also mean that you’re already diabetic, and you’re not controlling your blood sugar levels as well as you should. The longer a person’s A1C levels remain elevated, the greater their risk of developing side effects related to diabetes.

Higher A1C levels have been linked to increased risk of:

  • stroke and heart attack (cardiovascular disease)
  • kidney disease (nephropathy)
  • nerve damage (neuropathy)
  • eye damage that may result in blindness (retinopathy)

If your A1C value is high, your doctor and healthcare team will help you change your treatment plan to get your blood glucose levels under control.

Content licensed from:

Written by: Dale Kiefer
Medically reviewed on: Jun 08, 2016: University of Illinois-Chicago, College of Medicine

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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