Is the A1C Test Best for Diagnosing Diabetes?

By Vincent Savarese, MD, Virtua North Section Chief of Endocrinology

According to the Centers for Disease Control and Prevention, of the 29.1 million Americans with diabetes, 8.1 million are undiagnosed. Recently, the A1C test has emerged as an increasingly effective means of diagnosing diabetes and identifying pre-diabetes. The following helps answer some common questions about the A1C test.

What is the A1C test?

In the past, the standard diagnostic test for diabetes has been the fasting glucose test. However, the drawback of this test is that it requires the patient to fast for 12 hours. It also only reflects the patient’s blood glucose level at the time of testing—possibly missing some individuals who may have abnormal glucose levels. 

The A1C test stands for hemoglobin A1C. Hemoglobin is the protein on the red blood cell that binds with oxygen and delivers it to your tissues. Over the life of a red blood cell, sugar attaches to hemoglobin automatically. The amount of sugar that attaches to the hemoglobin is directly proportional to the amount of sugar in the blood stream. Because the life span of a red blood cell is about 3 – 4 months, the A1C test can tell you what a person’s average blood sugar level is over a period of about 3 months. 

Is this a new test?

The A1C test has been around for a long time. It has been used to monitor the progress of those who have already been diagnosed with type-1 or type-2 diabetes. 

In recent years, the A1C test has become more accurate and more standardized. That means that physicians can interpret the results with a greater accuracy than ever before. Because the A1C test can gauge a person’s blood glucose level over a period of about 3 months, it provides a more complete picture of the person’s status compared to the fasting glucose test alone. 

Ideally, your A1C level should be under 5.7%. If it’s at or above 5.7%, it means you have pre-diabetes (at risk for diabetes). If it’s 6.5% or higher, it means you have diabetes.

Should I get the test?

If you meet any of the following criteria, the A1C test may be recommended for you:

• Older than 40
• Diagnosed with high blood pressure or high cholesterol
• Have a BMI over 25
• Have other diabetes risk factors like a first-degree relative with diabetes, a history of gestational diabetes or polycystic ovary syndrome

If the A1C test shows that you’re in the borderline range for diabetes, that doesn’t mean you can’t take steps to improve your health. There’s evidence that you can reduce the risk of diabetes in the short term with a low-carb diet, increased exercise and a 5 to 7% reduction in body weight. In some cases, your doctor may recommend medication to manage your blood sugar or to reduce your diabetes risk. 

While use of the test is expanding, it may not always be included in a standard physical, so it’s worth asking your doctor your standard blood work includes an A1C test. 

The greatest benefit of the A1C test is that it empowers patients to make smart choices to protect their health. 

Updated June 14, 2018