What Is an A1C Test?

An A1C test can diagnose diabetes and monitor blood sugar levels over several months. It can also identify prediabetes, which raises your risk for diabetes.

A1C tests were first approved for use in the 1980s to monitor diabetes control. They are now widely used for the diagnosis and treatment of diabetes and are more important than ever before. That’s because, over the past 20 years, the number of Americans diagnosed with diabetes has more than doubled.

In all, more than 37 million American adults have diabetes (about 11 percent of the population), according to the Centers for Disease Control and Prevention (CDC). Nearly 2 million have type 1 diabetes, an autoimmune condition in which the pancreas makes no, or very little, insulin — the hormone that regulates blood glucose (also known as blood sugar).

The vast majority of Americans with diabetes have type 2 diabetes, a disease primarily caused by lifestyle factors (being overweight and sedentary). It occurs when cells don’t respond normally to insulin, causing blood sugar to rise.

What’s more, estimated 96 million people have prediabetes, marked by blood sugar that is higher than normal but not quite high enough for a type 2 diabetes diagnosis. It’s a warning, however, that you could be at elevated risk for developing diabetes unless you take action, such as becoming physically active, eating a nutritious diet, and getting excess weight under control.

Obviously, managing diabetes, and checking to see if you have prediabetes, involves knowing whether your blood sugar is too high and, especially, finding out if it is elevated over time.

The A1C test is a blood test that easily provides this information.

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Understanding an A1C test

The A1C test, sometimes referred to as a hemoglobin A1C or HbA1c test, uses a single blood sample to find your average blood sugar level over the course of about three months.

The test is performed in your doctor’s office or a lab using a sample of blood from a finger stick or from your arm. You don’t have to fast or do anything else out of the ordinary to prepare for your A1C test.

An A1C test measures the amount of sugar attached to certain blood cells. When sugar is in your bloodstream, it latches to hemoglobin, an oxygen carrying protein in red blood cells. While it’s true that everyone has some amount of sugar attached to their hemoglobin, you have significantly more if your blood sugar levels are higher than normal.

So, the AIC test analyzes your blood sample to find the percentage of your hemoglobin that is glycated (meaning how much hemoglobin has sugar attached to it) and uses the information to compute what your blood glucose level has been over about 90 days.

What A1C test results mean

There’s no exact, one-size-fits all target for normal A1C results, the American Diabetes Association points out. A1C levels can vary according to age and other factors.

There are guidelines for a range of A1C results, however. For example, if your A1C level is between 5.7 percent and less than 6.5 percent, you’re in the prediabetes range, and you need to work with your doctor to lower your blood sugar to avoid type 2 diabetes.

If you have an A1C level of 6.5 percent or higher, your level is in the range for a diagnosis of diabetes. For most adults already diagnosed with diabetes, an A1C test result of less than 7 percent is the goal for controlling the disease. The higher the level, the greater your risk of developing diabetes complications.

Find out if you need an A1C test

The CDC recommends a baseline A1C test if you’re an adult 45 or older. If your results are in the normal range but you have risk factors for diabetes, such as being overweight — or if you are a woman with a history of gestational diabetes — the CDC suggests repeating the A1C test every three years.

Even if you are younger but overweight, however, or have any other risk factors for prediabetes or type 2 diabetes (including having a parent, brother, or sister with type 2 diabetes, or you are physically active fewer than three times a week), talk to your doctor about having an A1C test.

If your A1C test shows you have prediabetes, work with your doctor on a plan to improve your health and lower your risk for type 2 diabetes with regular exercise and weight control. Your doctor will decide when to repeat the test to check your progress, typically every one or two years.

If you are diagnosed with diabetes, you usually get an A1C test every three months to make sure your blood glucose level is in the target range. If several A1C results reveal your diabetes is under good control, your doctor may decide you can wait longer between tests — usually at least twice a year.

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