The A1C test is a common blood test used in the management and diagnosis of diabetes. It provides information about an individual’s average blood glucose levels over an extended period, offering a long-term picture of blood sugar control.
What A1C Measures
The A1C test specifically measures glycated hemoglobin, also known as HbA1c. Hemoglobin, a protein in red blood cells, carries oxygen. When glucose is in the bloodstream, it can attach to hemoglobin in a process called glycation.
Once glucose binds to hemoglobin, it stays attached for the red blood cell’s lifespan. Red blood cells circulate for about 100 to 120 days, or two to three months. This lifespan means the A1C test reflects average blood sugar levels over that period. A higher amount of glucose attached to hemoglobin indicates higher average blood sugar levels.
How A1C is Determined
A1C determination begins with a blood sample, typically drawn from a vein in the arm, then sent to a laboratory. Some settings may use a finger-prick sample for monitoring, though venous blood is often preferred for diagnosis.
In the laboratory, specialized techniques like high-performance liquid chromatography (HPLC) or immunoassay measure the percentage of hemoglobin with glucose attached. These methods separate glycated from non-glycated hemoglobin to quantify the proportion bound to glucose. The result is expressed as a percentage.
Understanding Your A1C Results
Interpreting A1C results involves understanding specific percentage ranges for glucose control. For individuals without diabetes, an A1C level below 5.7% is considered normal. A result between 5.7% and 6.4% indicates prediabetes, suggesting a higher risk of developing type 2 diabetes.
An A1C of 6.5% or higher on two separate tests indicates diabetes. For those diagnosed, healthcare providers often aim for an A1C target of less than 7%, though individual goals may vary. A higher A1C percentage signifies higher average blood sugar levels, which can increase the risk of diabetes-related complications.
Factors Affecting A1C Accuracy
Several conditions can influence A1C test accuracy, potentially leading to inaccurate readings. Conditions affecting red blood cells, such as certain types of anemia, impact the test. For instance, iron-deficiency anemia or sickle cell anemia may cause falsely high or low A1C readings due to altered red blood cell lifespan or structure.
Recent significant blood loss or a blood transfusion can also affect A1C results by introducing new red blood cells. Kidney disease and liver disease can also influence A1C accuracy. Additionally, certain medications, specific genetic hemoglobin variants, and pregnancy can alter reliability.