What is A1c?

What is A1c?

Hemoglobin A1c is a blood test that is used to screen patients for prediabetes and diabetes.  It is also called the glycated hemoglobin level or the A1c level.   It is made when the high blood glucose levels attach themselves to hemoglobin, forming “sugar-coated” hemoglobin.  The greater the average glucose levels, the high is the amount of sugar-coating in the hemoglobin.

The Hemoglobin A1c level is a good screening test for both type 1 and type 2 diabetes.  It can’t be used, however, to screen for gestational diabetes or cystic fibrosis-related diabetes.  It can’t be used by anyone who has recently had a blood transfusion or has just developed the disease because it takes three months before the red blood cells to have glucose on the living cells.

Hemoglobin A1c test

People with anemia or hemoglobin variants will also be poor candidates for diabetic screening with a hemoglobin A1c level because their blood cell numbers are reduced.  Instead, a fasting blood sugar or an oral glucose tolerance test should be used to make the diagnosis of the disease.

Hemoglobin A1c as a Monitor for Diabetes

The hemoglobin A1c test can be used to monitor the amount of glucose control in diabetics over a period of time.  The test is usually only done once every 3 months because that is how long a red blood cell survives.  If the glucose is under control, it takes 3 months to see those changes reflected in the hemoglobin A1c.

Hemoglobin A1c monitor

As a monitor for elevated glucose levels on average, the hemoglobin A1c level can help prevent the complications of diabetes, such as kidney damage, nerve damage, eye damage, and heart disease.  When the hemoglobin A1c level is measured, it is a measurement of the average blood sugar levels within the past 2-3 months.

Ordering the Hemoglobin A1c Level

The hemoglobin A1c level can be done as part of diabetic screening in asymptomatic adults.  It may also be effective in diagnosing diabetes when the individual has symptoms of diabetes, including:

  • Blurry vision
  • Tiredness
  • Increased frequency of urination
  • Increased appetite
  • Increased thirst
  • Poorly-healing infections

People with risk factors can also be screened for diabetes with an A1c level. These include the following:

  • Genetic risk factors for diabetes
  • Obesity
  • Lack of physical activity
  • Being of a certain ethnicity
  • Having polycystic ovarian syndrome
  • Heart disease
  • High cholesterol levels
  • High blood pressure

Screening of obese individuals who are over the age of 45 years is recommended by checking the Hemoglobin A1c level.  The test should be repeated every 2-3 years, even if the first screening test was normal as diabetes could show up at a later date.


  1. Hemoglobin A1c. https://labtestsonline.org/understanding/analytes/a1c/tab/test/. Accessed 5/16/16.
Share Information and Help Others

Copy and paste this code to display the image on your site