how far back does a1c test go

The A1C test measures your average blood sugar levels over the past 2 to 3 months. This is because red blood cells, which carry hemoglobin, have a lifespan of about 3 months. The test calculates the percentage of hemoglobin that has glucose attached to it, providing a long-term view of blood sugar control.

• Why 2-3 months?: Red blood cells regenerate every 3 months, so the A1C test reflects your blood sugar levels during that period.
• Usefulness: It helps diagnose prediabetes, diabetes, and monitor how well your diabetes is being managed.

For more details, visit CDC's A1C Test Guide.