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April 16, 2021 / Alena Kharlamenko, MS, RD, CDN

What Is HbA1c and What Can It Show You?

Person getting their finger pricked by a nurse with white gloves on using a hbac1 blood test.

An HbA1c (Hemoglobin A1c) blood test is a valuable indicator of average blood sugar over the span of about three months. Blood tests in general can be useful for diagnosing a variety of conditions. Certain conditions may not have any noticeable signs or symptoms, so a blood test may be the first indication that something could be wrong. This is actually one of the reasons why prediabetes and type 2 diabetes often go undetected for years before being diagnosed. However, if diagnosed sooner, it may be possible to prevent or delay diabetes, and even reverse prediabetes.

Often, the HbA1c test is the wake-up call that some people need to make healthy lifestyle changes to prevent or manage diabetes, such as eating a balanced diet, exercising consistently, sleeping well, and focusing on stress management.

In this article, you’ll learn all about the HbA1c blood test, what it can tell you, and how it can be used to diagnose diabetes.

What Is Hemoglobin?

Hemoglobin is a protein in red blood cells that contains iron and helps blood carry oxygen throughout the body. Hemoglobin also transports carbon dioxide from parts of the body back to the lungs where it can be released. Red blood cells actually get their red coloring from the pigment in hemoglobin.

Hemoglobin levels are typically measured during a routine blood test to look for anemia or other blood disorders, such as thalassemia or sickle cell anemia.

Hemoglobin tests can indicate whether your levels are normal, low, or high. If your hemoglobin levels are low, your body has fewer red blood cells than normal and your cells might not be getting as much oxygen as they need. On the other hand, abnormally high hemoglobin levels may be a sign of a chronic illness such as heart disease or lung disease, or your body may be producing too many red blood cells.

There are many different types of hemoglobin—some of the most common normal types include:

There is also another hemoglobin that people are tested for called HbA1c, which we will cover extensively in this article.

What Is HbA1c?

HbA1c, also known as glycated hemoglobin, is produced when glucose in the blood attaches to hemoglobin. This causes hemoglobin to become glycated, hence the term “glycated hemoglobin.” It’s normal for some glucose to attach to your blood cells, but the problem occurs when excess glucose binds to hemoglobin and builds up in your blood.

HbA1c can be tested to determine your average blood sugar levels over a span of two to three months. Since red blood cells (hemoglobin) have a lifespan of about two to three months in the body before renewing, this test can be used as a good gauge of average blood glucose over that period of time.

The HbA1c test is what is used to diagnose diabetes and to monitor blood sugar levels of people at risk of developing diabetes and prediabetes. You might have seen this test referred to as hemoglobin A1c, glycated (or glycosylated) hemoglobin test, or simply even A1c—they all mean the same thing as HbA1c.

How Often Should I Take an HbA1c Test?

How often you should take an HbA1c test depends on your situation and what your doctor recommends. The Centers for Disease Control and Prevention (CDC) recommend the following testing frequency based on your scenario:

Signs You Should Take an HbA1c Test

There are some indicators that can point to the need to take an HbA1c test, whether they are signs of diabetes or risk factors to pay attention to.

You may also need to get your HbA1c tested if you are at risk for getting diabetes and have the following risk factors:

What Are the Normal HbA1c Levels?

Since the HbA1c test measures the percent of glucose attached to your hemoglobin, the results of the test are given in percentages. They can indicate whether your blood sugars are in the normal range, prediabetes range, or diabetes range. Based on your results, your doctor may recommend making some lifestyle or medication changes.

Normal range

Normal HbA1c levels are below 5.7%, with a normal range anywhere between 4% and 5.6%. A result of 5.6% or lower indicates that your estimated average glucose (eAG) levels are 114 mg/dL or lower.

Prevention is key to avoiding type 2 diabetes. Even if your HbA1c levels are normal, you could still be experiencing symptoms of insulin resistance, such as elevated fasting blood sugars, the development of skin tags and dark skin patches, and elevated triglyceride levels. In this case, you can take action before the insulin resistance progresses to prediabetes and type 2 diabetes.

Prediabetes range

The HbA1c prediabetes range is between 5.7% and 6.4% and suggests that you are at risk of developing type 2 diabetes. These results indicate that your estimated average glucose levels are between 117 mg/dL and 134 mg/dL.

About 88 million American adults have prediabetes, according to the CDC. That’s roughly one in three adults, so you’re certainly not alone. While it may be discouraging to receive these results, there are steps you can take to reverse prediabetes and avoid or delay the onset of type 2 diabetes.

It’s important to practice a healthy lifestyle that includes plenty of exercise and a nutrient-rich diet to avoid developing diabetes. A prediabetes diet plan can make it easier to adopt a balanced diet and help you lower blood sugar levels naturally.

Diabetes range

The diabetes range for the HbA1c test is at or above 6.5%. These levels indicate that your estimated average glucose levels are 140 mg/dL or higher. The goal for most people with diabetes is to keep their HbA1c level at or below 7%. The higher your HbA1c level, the higher your blood sugars are and the more at risk you are of developing diabetes-related complications.

If your HbA1c comes back in the diabetes range, your doctor will create a treatment plan to get your blood sugar into a normal range. You may also be referred to see other health care professionals, such as an endocrinologist, foot doctor, eye doctor, dietitian, and/or a diabetes educator.

What Is the Difference Between a Glucose Test and HbA1c?

Both a glucose test and a HbA1c are used to measure your blood sugars. However, these tests have quite a few differences:

The Takeaway

An HbA1c test can serve as a valuable indicator of your long-term average blood glucose levels. This is why it’s one of the tests used to determine if someone has prediabetes or type 2 diabetes.

Many tests, even an HbA1c home test, can be done in the comfort of your own home. Since some conditions (including diabetes) often don’t provide you with noticeable signs or symptoms, a blood test is important to get diagnosed early. If you want to skip the doctor’s visit at the moment, don’t hesitate to take an at-home blood test.

Once you know your HbA1c, you can take the appropriate steps to help prevent, delay, or manage type 2 diabetes. PlateJoy can help you plan healthy meals and lower your blood sugar levels.

Alena Kharlamenko, MS, RD, CDN
Registered Dietitian and Nutrition Consultant @ Alena Menko Nutrition

Alena Kharlamenko is the founder of Alena Menko Nutrition, a food and nutrition blog where she publishes healthful, plant-forward recipes and makes nutrition approachable with easily digestible information. She’s also passionate about gut health and is a Monash FODMAP-Trained Dietitian. When she's not cooking up a storm in the kitchen or behind her computer, she can be found exploring the vast culinary scene of NYC, traveling around the world, or hiking and spending time in nature. You can find Alena on Instagram @thebalancedbite or on Facebook @AlenaMenkoNutrition.

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