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.
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. 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. 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 www. Other names for the test include the glycosylated hemoglobin test, glycohemoglobin test, glycated hemoglobin test, or A1C. A1C measures the amount of hemoglobin in the blood that has glucose attached to it. Hemoglobin is a protein found inside red blood cells that carries oxygen to the body. Hemoglobin cells are constantly dying and regenerating. Their lifespan is approximately 3 months. Glucose attaches glycates to hemoglobin, so the record of how much glucose is attached to your hemoglobin also lasts for about 3 months.
If the amount of glucose is normal, your A1C will be normal. Someone without diabetes will have about 5 percent of their hemoglobin glycated. A normal A1C level is 5. A level of 5. People with diabetes have an A1C level of 6. The American Diabetes Association provides a calculator that shows how A1C levels correlate to glucose levels. To monitor overall glucose control, people with diabetes should have an A1C test at least twice a year.
The test is effective because of the lifespan of the hemoglobin cells. The glucose that was attached to the hemoglobin during the past 3 months will still be recorded by the test, since the cells live for approximately 3 months. The A1C test provides an average of your blood sugar readings for the past 3 months.
In the past, many different types of A1C tests gave different results depending on the lab that analyzed them. But the National Glycohemoglobin Standardization Program has helped improve the accuracy of these tests. Manufacturers of A1C tests now have to prove that their tests are consistent with those used in a major diabetes study. Accurate home test kits are also now available for purchase. But accuracy is relative when it comes to A1C or even blood glucose tests.
The A1C test result can be up to half a percent higher or lower than the actual percentage. That means if your A1C is 6, it might indicate a range from 5.
Some people may have a blood glucose test that indicates diabetes but their A1C is normal, or vice versa. Before confirming a diagnosis of diabetes, your doctor should repeat the test that was abnormal on a different day. Some people may get false results if they have kidney failure , liver disease , or severe anemia. Ethnicity can also influence the test. Your results may mean something different. If you have questions about your results, talk to your health care provider.
Your health care provider may have other recommendations for you, depending on your overall health, age, weight, and other factors. Learn more about laboratory tests, reference ranges, and understanding results.
The HbA1c test is not used for gestational diabetes , a type of diabetes that only affects pregnant women, or for diagnosing diabetes in children. Also, if you have anemia or another type of blood disorder , an HbA1c test may be less accurate for diagnosing diabetes. If you have one of these disorders and are at risk for diabetes, your health care provider may recommend different tests.
The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.
What is a hemoglobin A1c HbA1c test? Other names: HbA1c, A1c, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin. What is it used for? If you already have diabetes, an HbA1c test can help monitor your condition and glucose levels. Why do I need an HbA1c test? If you are under 45, you may need this test if you have certain risk factors. These include: Being overweight or obese High blood pressure History of heart disease Physical inactivity Testing should be done every 3 years, and more frequently if your results show you have prediabetes.
You may also need an HbA1c test if you have symptoms of diabetes. These include: Increased thirst Increased urination Blurred vision Fatigue.
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