Scientists Find Common Biological Basis for 5 Fatigue-Causing Illnesses

Hemoglobin A1c, commonly abbreviated as HbA1c or A1c, is a laboratory test that measures the average blood glucose level over approximately the past two to three months. This test is essential for diagnosing diabetes and monitoring how well blood sugar levels are being controlled in people who already have diabetes. Unlike regular blood glucose tests that provide a snapshot of sugar levels at a single moment, the A1c test offers a broader picture of glucose control over time. The test measures the percentage of hemoglobin proteins in red blood cells that have glucose attached to them, which occurs naturally when glucose circulates in the bloodstream.

The A1c test works because red blood cells live for about three months, and during their lifespan, glucose molecules bind to the hemoglobin inside them in a process called glycation. The higher the glucose levels in the blood, the more glucose attaches to hemoglobin. Since red blood cells have different lifespans, the A1c result primarily reflects average blood sugar levels from the past two to three months, with more recent weeks having slightly more influence on the result than earlier weeks. This makes the A1c test a valuable tool for healthcare providers to assess long-term glucose control rather than day-to-day fluctuations.

For diagnostic purposes, an A1c level below 5.7 percent is considered normal. A result between 5.7 and 6.4 percent indicates prediabetes, meaning blood sugar levels are higher than normal but not yet high enough to be classified as diabetes. An A1c level of 6.5 percent or higher on two separate occasions indicates diabetes. For people already diagnosed with diabetes, the general treatment goal is typically to maintain an A1c level below 7 percent, though individual targets may vary based on age, overall health, and other factors.

The A1c test offers several advantages over other glucose monitoring methods. It does not require fasting before the test, and it can be performed at any time of day, making it more convenient for patients. The test is not affected by short-term factors like stress, illness, or recent meals, which can cause temporary spikes or drops in blood glucose levels. However, certain conditions can affect A1c results, including anemia, recent blood transfusions, certain hemoglobin variants, kidney disease, and liver disease. In such cases, healthcare providers may use alternative tests or interpret results differently to ensure accurate assessment of glucose control.