Other names: HbA1C, A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin
→ Average blood sugar levels over past 3 months
→ to diagnose diabetes and prediabetes
→ to manage diabetes
What is the A1C test?
The A1C test—also known as the hemoglobin A1C or HbA1c test—is a simple blood test that measures your average blood sugar levels over the past 3 months. It’s one of the commonly used tests to diagnose prediabetes and diabetes, and is also the main test to help you and your health care team manage your diabetes. Higher A1C levels are linked to diabetes complications, so reaching and maintaining your individual A1C goal is really important if you have diabetes.
An A1C test can show your average glucose level for the past three months because:
→ Glucose sticks to hemoglobin for as long as the red blood cells are alive.
→ Red blood cells live about three months.
→ High A1C levels are a sign of high blood glucose from diabetes. Diabetes can cause serious health problems, including heart disease, kidney disease, and nerve damage. But with treatment and lifestyle changes, you can control your blood glucose levels.
What is glucose?
Glucose is a type of sugar in your blood that comes from the foods you eat. Your cells use glucose for energy. A hormone called insulin helps glucose get into your cells. If you have diabetes your body doesn't make enough insulin, or your cells don't use it well. As a result, glucose can't get into your cells, so your blood sugar levels increase.
Glucose in your blood sticks to hemoglobin, a protein in your red blood cells. As your blood glucose levels increase, more of your hemoglobin will be coated with glucose. An A1C test measures the percentage of your red blood cells that have glucose-coated hemoglobin.
What does the A1C test measure?
When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.
Who should get an A1C test and when?
Testing for diabetes or prediabetes:
Get a baseline A1C test if you’re an adult over age 45—or if you’re under 45, are overweight, and have one or more risk factors for prediabetes or type 2 diabetes:
→ If your result is normal but you’re over 45, have risk factors, or have ever had gestational diabetes, repeat the A1C test every 3 years.
→ If your result shows you have prediabetes, talk to your doctor about taking steps now to improve your health and lower your risk for type 2 diabetes. Repeat the A1C test as often as your doctor recommends, usually every 1 to 2 years.
→ If you don’t have symptoms but your result shows you have prediabetes or diabetes, get a second test on a different day to confirm the result.
→ If your test shows you have diabetes, ask your doctor to refer you to diabetes self-management education and support services so you can have the best start in managing your diabetes.
If you have diabetes, get an A1C test at least twice a year, more often if your medicine changes or if you have other health conditions. Talk to your doctor about how often it is right for you.
Your A1C Result:
A1C results tell you what percentage of your hemoglobin is coated with glucose. The percent ranges are just a guide to what is normal. What's normal for you depends on your health, age, and other factors. Ask your provider what A1C percentage is healthy for you.
If your A1C test was done to monitor your diabetes, talk with your provider about what your test results mean.
A normal A1C level is below 5.7%, a level of 5.7% to 6.4% indicates prediabetes, and a level of 6.5% or more indicates diabetes. Within the 5.7% to 6.4% prediabetes range, the higher your A1C, the greater your risk is for developing type 2 diabetes.
Normal → Below 5.7%
Prediabetes → 5.7% to 6.4%
Diabetes → 6.5% or above
What is the A1C test used for?
An A1C test may be used to screen for or diagnose:
Type 2 diabetes. With type 2 diabetes your blood glucose gets too high because your body doesn't make enough insulin to move blood sugar from your bloodstream into your cells, or because your cells stop responding to insulin.
Prediabetes. Prediabetes means that your blood glucose levels are higher than normal, but not high enough to diagnosed as diabetes. Lifestyle changes, such as healthy eating and exercise, may help delay or prevent prediabetes from becoming type 2 diabetes.
If you have diabetes or prediabetes, an A1C test can help monitor your condition and check how well you've been able to control your blood sugar levels.
Why do I need an HbA1C test?
The Centers for Disease Control (CDC) recommends A1C testing for diabetes and prediabetes if:
→ You are over the age 45.
→ If your results are normal, you should repeat the test every 3 years.
→ If your results show you have prediabetes, you will usually need to be tested every 1 to 2 years. Ask your provider how often to get tested and what you can do to reduce your risk of developing diabetes.
→ If your results show you have diabetes, you should get an A1C test at least twice a year to monitor your condition and treatment.
You are under 45 and are more likely to develop diabetes because you:
→ Have prediabetes.
→ Are overweight or obese
→ Have a parent or sibling with type 2 diabetes.
→ Have high blood pressure or high cholesterol levels.
→ Have heart disease or have had a stroke.
→ Are physically active less than 3 times a week.
→ Have had gestational diabetes (diabetes during pregnancy) or given birth to a baby over 9 pounds.
→ Are African American, Hispanic or Latino, American Indian, or an Alaska Native person. Some Pacific Islander and Asian American people also have a higher risk of developing diabetes.
→ Have polycystic ovarian syndrome (PCOS).
You may also need an A1C test if you have symptoms of diabetes, such as:
→ Feeling very thirsty
→ Urinating (peeing) a lot
→ Losing weight without trying
→ Feeling very hungry
→ Blurred vision
→ Numb or tingling hands or feet
→ Dry skin
→ Sores that heal slowly
→ Having more infections than usual
Is there anything else I need to know about an HbA1C test?
The A1C test is not used to diagnose gestational diabetes or type 1 diabetes.
Also, if you have a condition that affects your red blood cells, such as anemia or another type of blood disorder, an A1C test may not be accurate for diagnosing diabetes. Kidney failure and liver disease can also affect A1C results. In these cases, your provider may recommend different tests to diagnose diabetes and prediabetes.
Once you know your HbA1c level, it’s important that you understand what the results mean and how to stop them from getting too high. Even a slightly raised HbA1c level makes you more at risk of serious complications, so get all the facts here and be in the know about HbA1c.
Eyth E, Naik R. Hemoglobin A1C. [Updated 2023 Mar 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549816/
Aggarwal V, Schneider AL, Selvin E. Low hemoglobin A(1c) in nondiabetic adults: an elevated risk state? Diabetes Care. 2012 Oct;35(10):2055-60. doi: 10.2337/dc11-2531. Epub 2012 Aug 1. PMID: 22855733; PMCID: PMC3447844.
Pfister R, Sharp SJ, Luben R, Khaw KT, Wareham NJ. No evidence of an increased mortality risk associated with low levels of glycated haemoglobin in a non-diabetic UK population. Diabetologia. 2011 Aug;54(8):2025-32. doi: 10.1007/s00125-011-2162-0. Epub 2011 May 17. PMID: 21584793.
A low HgA1c may indicate that diabetes treatment is too aggressive. In people without diabetes, it is unclear whether a low HgA1c is harmful. Some researchers have found that low HbA1c may be problematic, while others have not. Compared with persons with normal HbA1c, low HbA1c values are associated with an increased risk of and death from various causes in some studies. Low HbA1c values generally reflect a level of chronic low blood sugar or hypoglycemia. There may be an increased risk of liver disease in people with low HbA1c.
An abnormally high level of HgA1c indicates chronic hyperglycemia, or high blood sugar. This is the definition of diabetes mellitus. Hemoglobin A1c is used to diagnose diabetes and track the effectiveness of diabetes treatments. Measurements at or above 6.5% are consistent with a diagnosis of diabetes. In most people with diabetes, the goal of treatment should be to have a hemoglobin A1c level less than 7%.
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