The hemoglobin A1C test is done to diagnose prediabetes, type 1, or type 2 diabetes. The A1C test does this by measuring the attachment of glucose to hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. In addition to diagnosing, the hemoglobin A1C also monitors how well blood sugar has been controlled over time.
The lower a patient’s hemoglobin A1C level is, the better controlled blood sugar has been over the last few months. Since this test shows the average blood sugar control over the last 2-3 months, it is more accurate than a blood glucose test, which only shows current blood sugar levels. A doctor may order a hemoglobin A1C test to determine baseline blood glucose averages, and then periodically to monitor those levels. This test is also called the A1C test, the Hba1c test, or the glycohemoglobin test.
The results are given as a percentage. The higher the percentage, the higher the blood sugar levels have been on average over the last 2-3 months. A percentage under 5.7% is normal. When being used to diagnose diabetes, an A1C level of 6.5 or higher on two separate occasions will result in a diabetes diagnosis. A result between 5.7-6.4 can be used to diagnose prediabetes. Prediabetes indicates a condition where the patient is more likely to develop diabetes if interventions in diet and exercise are not undertaken quickly.
For people who have already been diagnosed with diabetes, an A1C level of 7 is often a target. This depends on the individual, however, and a patient’s target will be determined by their physician. A level higher than the target may result in a change of therapy, in order to avoid complications of uncontrolled diabetes. Studies have shown that individuals who keep an A1C level under 7 percent are less likely to develop complications due to diabetes.
There are some factors that can limit the effectiveness of the hemoglobin A1C test. If a patient experiences heavy or chronic bleeding, this could cause levels to be artificially low. If a patient has iron-deficiency anemia, levels could be artificially high. Most people only have one type of hemoglobin, but some people groups have a hemoglobin variant, or uncommon form of hemoglobin. Hemoglobin variants are most often found in people with African or Southeast Asian heritage. These variants can be tested through another lab test.