A1C Test & Diabetes: Overview, Procedure, Levels, Chart.


For several decades, the diagnostic criteria for diabetes have been based on glycemic values such as fasting blood sugar or after glucose intake (glucose tolerance test-GTT). In 2010, the American Diabetes Association (ADA) approved the use of glycated hemoglobin as a diagnostic tool for diabetes and prediabetes based on recommendations from a panel of international experts including a representative from the ADA, of the International Diabetes Federation (IDF) and the European Association For the study Diabetes (EADS). The Swiss Society of Endocrinology (SSED) recently approved the application of this recommendation in Switzerland

What is the A1C test?

Hemoglobin A1c tests can be used to diagnose diabetes when testing is done by a certified laboratory (not the doctor’s office) People with a hemoglobin A1c level of 6-5% or higher are diabetic. If the rate is between 5.7 and 6.4, they are prediabetes and are at risk of developing diabetes. 

What is the A1C test

Hemoglobin is the red oxygen-carrying substance in red blood cells. When blood is exposed to high glucose levels for a prolonged period, glucose binds to hemoglobin and forms glycosylated hemoglobin. The blood hemoglobin A1c level is reported as a percentage of hemoglobin A1c. This process involves a healthcare professional who will convey it to a laboratory for evaluation.

Doctors may order this test to diagnose diabetes and to monitor blood sugar levels in people with diabetes to see how well treatment is working. If you are taking insulin or other drugs to treat diabetes, your doctor may also ask you about ways to monitor your blood sugar levels at home. This can be done using a glucometer or continuous blood sugar monitor. In this case, you will still need to undergo regular A1c testing. Normal values traditionally, A1c values are expressed as a percentage, alternatively, the doctor may report the A1c result as estimated average glucose(eAG), milligrams per decilitre (mg/dL), or millimoles per liter (mmol/L)

Benefits of A1c test

Good blood sugar control aims to prevent or delay the complications of diabetes. Blood sugar levels taken by the diabetic person themselves as well as glycated hemoglobin (A1C) make it possible to check glycemic control. The evaluation of average glycemic control in diabetics is possible thanks to the measurement of glycated hemoglobin (HB1Ac). Recently, new recommendations have been issued giving this assay value as a diagnostic test for diabetes. HbA1c has the advantage of being the best parameter for predicting diabetes complications. It is measurement is relatively reliable and simple 

Hemoglobin A1c

Doctors can monitor treatment using a blood test called a hemoglobin A1c test. When blood sugar levels are high, hemoglobin, the protein that carries oxygen in the blood, is changed. These changes are directly proportional to blood sugar levels, over a long period of time. The higher the hemoglobin A1c level, the higher the person’s blood sugar levels were thus, unlike measuring blood sugar which indicates a point value. Measuring hemoglobin A1c indicates whether blood sugar has been well controlled over the previous months.

In diabetics, the target hemoglobin A1c level is less than 7%. Reaching this level is something difficult, but the lower the hemoglobin A1c level, the lower the risk of developing complications. Doctors may recommend a slightly higher or lower target for some people based on their particular medical situation. However, rates above 9% indicate poor control, and rates above 12% indicate very poor control. Most diabetologists recommend checking hemoglobin A1c every 3 to 6 months.

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This is how the A1c test works

The A1c test is also known as the hemoglobin A1c or HbA1c test, glycated hemoglobin test, or glycated hemoglobin test. The A1c test measures the percentage of red blood cells that contain hemoglobin coated with glucose. This measurement allows the doctor to know the person’s average blood sugar levels over the past two to three months. A protein that is highly rich in iron known as hemoglobin is found in the red blood cells. It helps transport oxygen from the lungs to other tissues. When glucose enters the blood, it combines with hemoglobin. The more glucose in a person’s bloodstream, the more hemoglobin binds to glucose.

Target levels in people with diabetes

There are many factors by which a doctor will set the target level for an individual A1c. The appropriate set target varies from patient to patient. For diabetic patients, the target level may depend on their age, their health status, diabetes duration history, pregnancy, prescribed treatment plan, any history of adverse effects from the cure, coupled with various history of hypoglycemia, whatever difficulties from past diabetes history, individual preferred type of medication, based on this priorities, a medical professional might target an A1c level below 6.5% if a person is young and has a long life expectancy has had diabetes for a short period, is effectively controlling the diabetic condition through change of lifestyle or recommended drug and otherwise in good health.

A doctor might recommend A1c targets of 7.0-8.5%. If a person: is older and has a shorter life expectancy, has had diabetes for a longer period, has diabetes that is difficult to control despite diverse prescribed drugs, is known for chronic low sugar levels problems, or other complicated past treatments, has in the past suffered diabetes or other complicated health challenges. For clinical reevaluation, an individual can approach their healthcare specialists for adjustment in their A1c target level time. However, the intention for the treatment and the purpose may change.

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A1c level by age is one of the many factors that affect a person’s blood sugar levels. Blood sugar levels also rise with age, but the changes are often small. HbA1c is now a screening tool for diabetes validated by export diabetology societies and has many interesting advantages and characteristics. However, the HbA1c measurement must be done using a standardized measurement and the result interpreted taking into account the different interpretation limits.

Hemoglobin A1c test for protein, doctors can also measure the level of a protein in the blood, hemoglobin A1c  (also called glycated or glycosylated hemoglobin). It reflects long-term trends in a person’s blood sugar levels rather than rapid changes.


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  • Little RR, Rohlfing CL. The long and winding road to optimal HbA1c measurement. Clin Chim Acta 2013; 418:63–71. CrossRef

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    Dr. David G Kiely is a distinguished Medical Reviewer and former General Medicine Consultant with a wealth of experience in the field. Dr. Kiely's notable career as a General Medicine Consultant highlights his significant contributions to the medical field.

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