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Overview

What Is an HbA1c Blood Test?

An HbA1c blood test measures glycated hemoglobin, also called hemoglobin A1c. Glucose in the blood attaches to hemoglobin inside red blood cells, and the HbA1c result estimates your average blood glucose level over the previous 2 to 3 months. Unlike a single blood glucose reading, it does not show only the level at the exact time your blood is drawn.

When It Is Needed

When Is an HbA1c Test Needed?

A clinician may order an HbA1c test if symptoms or other findings suggest diabetes. It may also be used as routine blood screening for diabetes in people with certain age-related or personal risk factors, or repeated at intervals to monitor treatment and blood glucose control after a diabetes diagnosis.

  • Increased thirst or frequent urination
  • Overweight or obesity
  • A family history of type 2 diabetes
  • A history of gestational diabetes
  • An existing diagnosis of diabetes
  • Other blood test results or symptoms that raise concern about diabetes

Preparation

How to Prepare for an HbA1c Blood Test

Fasting is usually not required for a hemoglobin blood test such as an HbA1c test. If other blood tests are being collected at the same appointment, follow the laboratory’s instructions because those tests may have different preparation requirements.

During the Test

What Happens During the HbA1c Test?

A healthcare professional cleans the skin and collects a small blood sample, usually from a vein in your arm. Some facilities may collect the sample with a finger stick instead. The sample is then sent to a laboratory or analyzed using an approved testing device.

The collection is usually brief and may cause a momentary pinch or sting. Mild tenderness or a small bruise can occur afterward, but most people can return to their usual activities after the test.

Risks

What Are the Risks of an HbA1c Blood Test?

  • Brief stinging or pinching when the needle enters
  • Mild soreness at the puncture site
  • A small bruise
  • A small amount of bleeding
  • Temporary dizziness or faintness

After the blood draw

When to seek advice

Contact a healthcare professional if bleeding does not stop, swelling increases, pain is severe, or the puncture site becomes red, warm, increasingly painful, or produces drainage.

Results

Understanding HbA1c Test Results

An HbA1c report may show the result as a percentage and/or in mmol/mol. The categories below are general interpretation thresholds used for adults and are not a substitute for discussing your diabetes test results with a clinician.

Result categoryHbA1c percentageWhat it may indicate
Below prediabetes rangeBelow 5.7% (below 39 mmol/mol)Usually not in the prediabetes or diabetes range
Prediabetes range5.7% to 6.4% (39 to 46 mmol/mol)Higher risk of developing type 2 diabetes
Diabetes range6.5% or higher (48 mmol/mol or higher)May indicate diabetes and usually requires clinical confirmation

An individual HbA1c target for diabetes management may differ from these screening thresholds. It can depend on your age, whether you are pregnant, other health conditions, your treatment plan, and your risk of low blood glucose. Anemia, unusual blood conditions, recent blood loss, or a transfusion can also affect the accuracy of the result, so your clinician will interpret it in context.

Diseases & Conditions

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