A1C test
`
`Overview
`
`The A1C test is a common blood test used to diagnose type 1 and type 2 diabetes. If you're living with diabetes, the test is also used to monitor how
`well you're managing blood sugar levels. The A1C test is also called the glycated hemoglobin, glycosylated hemoglobin, hemoglobin A1C or HbA1c
`test.
`
`An A1C test result reflects your average blood sugar level for the past two to three months. Specifically, the A1C test measures what percentage of
`hemoglobin proteins in your blood are coated with sugar (glycated). Hemoglobin proteins in red blood cells transport oxygen.
`
`The higher your A1C level is, the poorer your blood sugar control and the higher your risk of diabetes complications.
`Why it's done
`
`The results of an A1C test can help your doctor or other health care provider:
`Diagnose prediabetes. If you have prediabetes, you have a higher risk of developing diabetes and cardiovascular disease.
`Diagnose type 1 and type 2 diabetes. To confirm a diabetes diagnosis, your doctor will likely look at the results of two blood tests given on
`different days — either two A1C tests or the A1C test plus another test, such as a fasting or random blood sugar test.
`Monitor your diabetes treatment plan. The result of an initial A1C test also helps establish your baseline A1C level. The test is then repeated
`regularly to monitor your diabetes treatment plan.
`
`How often you need the A1C test depends on the type of diabetes, your treatment plan, how well you're meeting treatment goals and your primary care
`doctor's clinical judgment. For example, the A1C test may be recommended:
`
`Once every year if you have prediabetes
`Twice a year if you don't use insulin and your blood sugar level is consistently within your target range
`Four times a year if you take insulin or have trouble keeping your blood sugar level within your target range
`
`You may need more-frequent A1C tests if your doctor changes your diabetes treatment plan or you begin taking a new diabetes medication.
`How you prepare
`
`The A1C test is a simple blood test. You don't need to fast for the A1C test, so you can eat and drink normally before the test.
`What you can expect
`
`During the A1C test, a member of your health care team takes a blood sample by inserting a needle into a vein in your arm or pricking your finger tip
`with a small, pointed lancet. If the blood is taken from a vein, the blood sample is sent to a lab for analysis.
`
`Blood from a finger prick may be analyzed in your doctor's office for same-day results. This in-office test is only used for monitoring your treatment plan,
`not for diagnosis or screening.
`Results
`
`A1C test results are reported as a percentage. A higher A1C percentage corresponds to higher average blood sugar levels. Results for a diagnosis are
`interpreted as follows:
`
`Below 5.7% is normal.
`5.7% to 6.4% is diagnosed as prediabetes.
`6.5% or higher on two separate tests indicates diabetes.
`
`For most adults living with diabetes, an A1C level of less than 7% is a common treatment target. Lower or higher targets may be appropriate for some
`people.
`
`The target of less than 7% is associated with a lower risk of diabetes-related complications. If your A1C level is above your target, your doctor may
`recommend an adjustment in your diabetes treatment plan.
`A1C and self-monitoring
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`A part of your treatment plan will include self-monitoring at home with a blood glucose meter or other device. Your health care team will direct you on
`how often and when you should test your blood sugar.
`
`Your self-monitoring device reports your blood sugar levels in milligrams of sugar per deciliter (mg/dL) or millimoles of sugar per liter (mmol/L). The
`measurement shows your blood sugar level at the time you do the test. Therefore, there is some variability throughout the day based on eating,
`exercise, stress and other factors.
`
`Self-monitoring helps you make choices about diet and exercise and daily treatment goals, but it also helps you track whether you are meeting your
`A1C target. For example, if your A1C target is below 7%, your self-monitoring blood sugar levels should be, on average, below 154 mg/dL (8.6
`mmol/L).
`
`A1C test results generally correspond with the following results of blood sugar levels:
`
`A1C level
`
`Estimated average blood sugar (glucose) level
`
`6%
`
`7%
`
`8%
`
`9%
`
`10%
`
`11%
`
`12%
`
`126 mg/dL (7 mmol/L)
`
`154 mg/dL (8.6 mmol/L)
`
`183 mg/dL (10.2 mmol/L)
`
`212 mg/dL (11.8 mmol/L)
`
`240 mg/dL (13.4 mmol/L)
`
`269 mg/dL (14.9 mmol/L)
`
`298 mg/dL (16.5 mmol/L)
`
`Limitations of the A1C test
`Some factors may interfere with the accuracy of A1C test results. These include:
`
`Pregnancy
`Recent or heavy blood loss
`Recent blood transfusion
`Conditions that result in insufficient red blood cells (anemias)
`Hemoglobin variants
`
`The most common form of the oxygen-transporting hemoglobin protein is called hemoglobin A. The presence of other variants of the protein may result
`in inaccurate A1C test results. Hemoglobin variants are more common among people of African, Mediterranean or Southeast Asian descent.
`
`If you have a hemoglobin variant, your test may need to be sent to a specialized lab or you may need a different test for diagnosis and monitoring of
`diabetes.
`
`By Mayo Clinic Staff
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