If you have risk factors for prediabetes or diabetes , talk with your doctor about whether you should be tested. Health care professionals can use the A1C test alone or in combination with other diabetes tests to diagnose type 2 diabetes and prediabetes.

When using the A1C test for diagnosis, your doctor will send your blood sample taken from a vein to a lab that uses an NGSP-certified method. The NGSP , formerly called the National Glycohemoglobin Standardization Program, certifies that makers of A1C tests provide results that are consistent and comparable with those used in the Diabetes Control and Complications Trial.

The A1C test should not be used to diagnose type 1 diabetes , gestational diabetes , or cystic fibrosis -related diabetes. The A1C test may give false results in people with certain conditions. Having prediabetes is a risk factor for developing type 2 diabetes.

Within the prediabetes A1C range of 5. Health care professionals may use the A1C test early in pregnancy to see if a woman with risk factors had undiagnosed diabetes before becoming pregnant.

Since the A1C test reflects your average blood glucose levels over the past 3 months, testing early in pregnancy may include values reflecting time before you were pregnant. The glucose challenge test or the oral glucose tolerance test OGTT are used to check for gestational diabetes , usually between 24 and 28 weeks of pregnancy.

If you had gestational diabetes, you should be tested for diabetes no later than 12 weeks after your baby is born. If your blood glucose is still high, you may have type 2 diabetes. Even if your blood glucose is normal, you still have a greater chance of developing type 2 diabetes in the future and should get tested every 3 years.

Health care professionals also use the fasting plasma glucose FPG test and the OGTT to diagnose type 2 diabetes and prediabetes. For these blood glucose tests used to diagnose diabetes , you must fast at least 8 hours before you have your blood drawn.

In some cases, health care professionals use the A1C test to help confirm the results of another blood glucose test. In some people, a blood glucose test may show diabetes when an A1C test does not. The reverse can also occur—an A1C test may indicate diabetes even though a blood glucose test does not.

Because of these differences in test results, health care professionals repeat tests before making a diagnosis. People with differing test results may be in an early stage of the disease, when blood glucose levels have not risen high enough to show up on every test.

In this case, health care professionals may choose to follow the person closely and repeat the test in several months. Lab test results can vary from day to day and from test to test.

This can be a result of the following factors:. Your results can vary because of natural changes in your blood glucose level. For example, your blood glucose level moves up and down when you eat or exercise.

Sickness and stress also can affect your blood glucose test results. A1C tests are less likely to be affected by short-term changes than FPG or OGTT tests. The following chart shows how multiple blood glucose measurements over 4 days compare with an A1C measurement.

The straight black line shows an A1C measurement of 7. The blue line shows an example of how blood glucose test results might look from self-monitoring four times a day over a 4-day period. Conditions that change the life span of red blood cells, such as recent blood loss, sickle cell disease , erythropoietin treatment, hemodialysis , or transfusion, can change A1C levels.

A falsely high A1C result can occur in people who are very low in iron; for example, those with iron-deficiency anemia. Other causes of false A1C results include kidney failure or liver disease. People in these groups may have a different type of hemoglobin, known as a hemoglobin variant, which can interfere with some A1C tests.

Most people with a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin. Not all A1C tests are unreliable for people with a hemoglobin variant. People with false results from one type of A1C test may need a different type of A1C test to measure their average blood glucose level.

The NGSP provides information for health care professionals about which A1C tests are appropriate to use for specific hemoglobin variants. Read about diabetes blood tests for people of African, Mediterranean, or Southeast Asian descent.

Even when the same blood sample is repeatedly measured in the same lab, the results may vary because of small changes in temperature, equipment, or sample handling. These factors tend to affect glucose measurements—fasting and OGTT—more than the A1C test.

Health care professionals understand these variations and repeat lab tests for confirmation. Diabetes develops over time, so even with variations in test results, health care professionals can tell when overall blood glucose levels are becoming too high. When repeated, the A1C test result can be slightly higher or lower than the first measurement.

This means, for example, an A1C reported as 6. Health care professionals can visit ngsp. org to find information about the precision of the A1C test used by their lab. Your health care professional may use the A1C test to set your treatment goals, modify therapy, and monitor your diabetes management.

Experts recommend that people with diabetes have an A1C test at least twice a year. People will have different A1C targets, depending on their diabetes history and their general health. You should discuss your A1C target with your health care professional.

Studies have shown that some people with diabetes can reduce the risk of diabetes complications by keeping A1C levels below 7 percent. Managing blood glucose early in the course of diabetes may provide benefits for many years to come.

The higher the percentage, the higher your blood glucose levels over the past two to three months. The A1C test can also be used for diagnosis, based on the following guidelines:.

Another term you may come across when finding out your A1C is eAG. Your doctor might report your A1C results as eAG. eAG is similar to what you see when monitoring your blood glucose at home on your meter.

However, because you are more likely to check your blood glucose in the morning and before meals, your meter readings will likely be lower than your eAG. More about A1C and eAG Learn how diabetes is diagnosed. Breadcrumb Home About Diabetes Understanding A1C. Understanding A1C.

The big picture: monitoring treatment This relatively simple blood test can tell you a lot. So, what do the numbers mean? The A1C test can also be used for diagnosis, based on the following guidelines: Image.

Read More.