Definition & Overview

The hemoglobin A1C test is the primary diagnostic procedure that determines the patient's average sugar level for the past two to three months. It is performed to diagnose diabetes, determine the type of diabetes the patient has, and for patients who are already receiving treatment, this blood test is used determine the efficacy of their medications in keeping their sugar levels under control.

Sugar or glucose has the tendency to coat the hemoglobin, the protein in red blood cells that carries oxygen throughout the body. When this happens, it leads to the formation of glycated hemoglobin. The higher the amount of sugar in the blood, the more glycated hemoglobin is formed. The sugar that coats the hemoglobin protein gets thicker when the sugar level in the body rises.

The hemoglobin A1C test measures the amount of glycated hemoglobin in the blood for the past three months, which is the lifespan of the red blood cells. Anything that is lower than 5.9% is considered normal while 6% means that the patient is at risk of developing diabetes. Meanwhile, beyond 7 percent not only indicates the presence of diabetes but also higher risks of developing diabetic complications like nerve problems, vision loss, and cardiovascular diseases.

Who Should Undergo and Expected Results

The hemoglobin A1C test is recommended for:

  • Diabetic patients who need to control their blood sugar level. Among newly diagnosed diabetics, this test is prescribed to determine the extent of their condition and the efficacy of the initial treatment they received. Even those who are just starting to experience the associated symptoms may also be advised to undergo this test to determine whether they have type 1 or type 2 diabetes. This is important as this is the first step in identifying the best treatment method for their condition.

  • Patients deemed at risk of developing diabetes – These include overweight individuals who are physically inactive, hypertensive, have close relatives with diabetes, or have low HDL cholesterol and/or high triglycerides levels.

  • Women with polycystic ovary syndrome, especially if they are also overweight, as their condition puts them at a higher risk of developing diabetes.

This test is not indicated for those with anemia, severe kidney disease, or for individuals who had blood transfusion in the last three months as these affect the level of hemoglobin in the body and may cause unreliable and inaccurate results.

There are no known problems or issues associated with hemoglobin A1C test and it can be prescribed to both children and adults. The number of times this procedure is carried out is affected by several factors. For example, individuals who are suspected of having prediabetes condition are typically asked to take the test once a year for monitoring purposes. Meanwhile, those diagnosed with type 2 diabetes must undergo the test twice a year and for patients with type 1 diabetes or are taking insulin, quarterly hemoglobin A1C tests are required.

If test results indicate an unusually high percentage of glycated hemoglobin, the physician may prescribe a higher dosage of medication or switch to a different treatment method and advise patients to be more aggressive in managing this condition. This may mean a radical shift in lifestyle to promote wellness and increased frequency and amount of exercise to stave off complications particularly those that are life-threatening.

Patients with borderline results are typically asked to constantly monitor their sugar intake to help them avoid developing full-blown diabetes.

How is the Procedure Performed?

The test requires drawing blood from the patient which can be done by inserting a needle into a vein in the arm or pricking the tip of the finger using a lancet. To collect blood from the arm, the vein is exposed by wrapping the upper arm with an elastic band. After swabbing the injection site with alcohol, the needle is inserted and attached to a tube where the blood is stored. Certain cases require medical personnel to perform blood extraction more than once to obtain the appropriate amount. After removing the needle, pressure is applied to the site to stop bleeding and a bandage is used.

The collected blood is then sent to a laboratory for analysis and the results, which are forwarded to the patient’s attending physician, are typically made available after a few days.

Possible Risks and Complications

Hemoglobin A1c test is a safe procedure. However, there is a small risk that patients may experience the following:

  • Bleeding at the injection site. To prevent more serious bleeding-related problems, patients are advised to inform medical professionals beforehand if they are taking blood thinners or have existing bleeding conditions.

  • A slight bruise or hematoma may develop on the injection site, though this typically goes away after a few days.

  • Some patients may experience phlebitis or swelling of the vein following blood extraction, which can be resolved by applying warm compress on the site.


  • Chan CL, Pyle L, Newnes L, Nadeau KJ, Zeitler PS, Kelsey MM. Continuous glucose monitoring and its relationship to hemoglobin A1c and oral glucose tolerance testing in obese and prediabetic youth. J Clin Endocrinol Metab. 2015 Mar. 100 (3):902-10
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