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What is a Hemoglobin A1C (HbA1C) Test?

A hemoglobin A1C (HbA1C) test is a simple blood test that provides an average of your blood sugar (glucose) levels over the past two to three months.

Glucose, the main type of sugar in your blood, comes from the food you eat and is used by your cells for energy. Insulin, a hormone made by the pancreas, helps glucose enter your cells. If you have diabetes, your body either doesn’t produce enough insulin or doesn’t use it effectively. This leads to higher glucose levels in the blood.

When glucose builds up in your blood, it attaches to hemoglobin — the protein in red blood cells that carries oxygen. The A1C test measures the percentage of hemoglobin coated with glucose, giving an average of your blood sugar over the life span of your red blood cells (about three months).

Other Names

HbA1C, A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin

What is it Used For?

Unlike daily blood sugar checks, which only measure glucose at a single point in time, the A1C test gives a long-term picture of your average blood glucose. It may be used to:

  • Screen for or diagnose type 2 diabetes: Occurs when the body doesn’t make or use insulin well, leading to high blood sugar.
  • Detect prediabetes: Higher-than-normal blood sugar levels, but not yet diabetes. Lifestyle changes can often prevent progression.
  • Monitor diabetes management: Helps determine how well blood glucose has been controlled over time.

While not used to diagnose type 1 diabetes, the A1C test may still help monitor blood glucose in people with type 1.

Why Do I Need an A1C Test?

The CDC recommends A1C testing for people at risk of or living with diabetes:

  • Age 45 or older: Even if results are normal, repeat testing intervals depend on risk factors and provider advice.
  • Prediabetes: Testing usually every 1–2 years.
  • Diabetes: Testing at least twice a year to monitor treatment and control.
  • Under 45 with risk factors: Includes being overweight, inactive, having high blood pressure or cholesterol, family history, or belonging to certain ethnic groups (e.g., African American, Hispanic/Latino, American Indian, Alaska Native, some Pacific Islander and Asian American groups).

Possible Symptoms Indicating the Need for Testing

  • Excessive thirst
  • Frequent urination
  • Unexplained weight loss
  • Constant hunger
  • Blurred vision
  • Numbness or tingling in hands or feet
  • Fatigue
  • Dry skin
  • Slow-healing sores
  • Frequent infections

What Happens During an A1C Test?

A healthcare professional draws a small blood sample from a vein in your arm using a needle. The process usually takes less than five minutes, with only minor discomfort.

Do I Need to Prepare for the Test?

No special preparation is required. However, certain medications (such as opioids and some HIV treatments) may affect results, so let your provider know what you’re taking. Pregnancy can also impact results.

Are There Any Risks?

Risks are minimal. Some people experience slight pain or bruising where the needle is inserted, but this usually fades quickly.

What Do the Results Mean?

The A1C test result shows the percentage of hemoglobin coated with glucose. Your provider will interpret results based on your health, age, and risk factors.

  • Normal: A1C below 5.7%
  • Prediabetes: A1C between 5.7% and 6.4%
  • Diabetes: A1C of 6.5% or higher

If your results are higher than normal, your provider may confirm with another A1C test or a different type of glucose test, such as a fasting blood glucose or an oral glucose tolerance test.

Other Important Considerations

The A1C test is not used to diagnose gestational diabetes. Additionally, certain conditions — such as anemia, kidney failure, or liver disease — may affect results. In these cases, your provider may recommend other tests for diagnosing or monitoring diabetes.