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Since 1990, Defeat Diabetes Foundation has been recommending that individuals with diabetes and those at risk for developing Type 2 diabetes have a regular A1c test, also known as HbA1c, performed by their doctor.
What is the A1C test?
The A1c test is a blood test that provides information about a person’s average levels of blood glucose, also called blood sugar, over the past 3 months. The A1C test is sometimes called the hemoglobin A1c, HbA1c, or glycohemoglobin test. The A1C test is the primary test used for diabetes management and diabetes research.
How does the A1C test work?
The A1C test is based on the attachment of glucose to hemoglobin, the protein in red blood cells that carries oxygen. In the body, red blood cells are constantly forming and dying, but typically they live for about 3 months. Thus, the A1C test reflects the average of a person’s blood glucose levels over the past 3 months. The A1C test result is reported as a percentage. The higher the percentage, the higher a person’s blood glucose levels have been. A normal A1C level is below 5.7 percent.
Can the A1C test be used to diagnose type 2 diabetes and prediabetes?
Yes. In 2009, an international expert committee recommended the A1C test as one of the tests available to help diagnose type 2 diabetes and prediabetes.1Previously, only the traditional blood glucose tests were used to diagnose diabetes and prediabetes.
Because the A1C test does not require fasting and blood can be drawn for the test at any time of day, experts are hoping its convenience will allow more people to get tested—thus, decreasing the number of people with undiagnosed diabetes. However, some medical organizations continue to recommend using blood glucose tests for diagnosis.
1The International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32(7):1327–1334.
The HbA1c, or A1c test, measures the amount of glycated hemoglobin present in your blood. During the 120-day life span of a red blood cell, glycated hemoglobin is formed when glucose molecules interact with hemoglobin.
Once a hemoglobin molecule is glycated, it stays that way for the rest of its lifecycle. Glycated hemoglobin reflects the average level of glucose to which the cell has been exposed during its life cycle.
The A1c test measures your blood sugar control over an 8 - 12 week period. It can give a good estimate of how well you have managed your diabetes over that time period. In individuals with poorly controlled diabetes, the quantities of these glycated hemoglobins are much higher than in healthy people.
The HbA1c test is recommended for checking blood sugar control in people who might be pre-diabetic and may help to determine if they actually have diabetes and for monitoring blood sugar control in patients with diabetes. In general, the reference range (that found in healthy persons), is about 4%-5.9%.
In most cases the A1c is the definitive test for diabetes and provides much more information for the doctor than a fasting blood sugar level. However, some people with shortened red blood cell life spans, such as anemia or sickle-cell disease, or any other condition causing premature red blood cell death, may not test definitively for diabetes with the A1c.
In general, the higher your HbA1c, the higher the risk that you may develop problems such as:
This is especially true if your HbA1c remains high for a long period of time. The closer your HbA1c is to normal, the less risk you have for these complications.
Defeat Diabetes Foundation recommends testing people with diabetes every 3 - 4 months.
Abnormal results mean that your blood glucose levels have not been well controlled over a period of weeks or months. If your HbA1c is above 7%, it means that you may have diabetes or your diabetes control may not be as good as it should be.
High values mean you are at greater risk of diabetes complications. If you can bring your level down, you decrease your chances of long-term complications.
While diabetic patient treatment goals vary, many include a target range of HbA1c values. A diabetic person with good glucose control has an HbA1c level that is close to or within the reference range. The International Diabetes Federation and American College of Endocrinology recommend HbA1c values below 6.5.
A high HbA1c represents poor glucose control. However, a "good" HbA1c level in a patient with diabetes can still be punctuated by a history of recent hypoglycemia, or spikes of hyperglycemia. Daily blood glucose monitoring is still the best method for evaluating overall health with respect to blood glucose control.
Here's how A1C level corresponds to average blood sugar level, in milligrams per deciliter (mg/dL) and millimoles per liter (mmol/L):
Estimated average blood sugar level
97 mg/dL (5.4 mmol/L)
126 mg/dL (7 mmol/L)
154 mg/dL (8.5 mmol/L)
183 mg/dL (10.2 mmol/L)
212 mg/dL (11.8 mmol/L)
240 mg/dL (13.3 mmol/L)
269 mg/dL (14.9 mmol/L)
298 mg/dL (16.5 mmol/L)
326 mg/dL (18.1 mmol/L)
355 mg/dL (19.7 mmol/L)
Sources: National Diabetes Information Clearing House (NDIC)