What Is A1C and Why It Matters

The A1C test (also known as the hemoglobin A1c, HbA1c, or glycated hemoglobin test) is a common blood test used to diagnose type 1 and type 2 diabetes and prediabetes.

It's also used to monitor how well someone with diabetes is managing their blood sugar levels over time.

Glucose (sugar) in your bloodstream sticks to hemoglobin, the protein in your red blood cells that carries oxygen.

The A1C test measures the percentage of your red blood cells that have glucose-coated hemoglobin.

Those with high blood sugar have a higher percentage of blood cells that have glucose-coated hemoglobin compared to people with lower blood sugar levels.

Red blood cells live for about 3 months, so the A1C test provides an average picture of your blood sugar levels over the preceding 2 to 3 months.

A higher A1C percentage means your average blood sugar levels have been higher during that period.