A1C

What it generally measures

Glucose in the bloodstream can attach to hemoglobin in red blood cells. A1C estimates the percentage of hemoglobin that is glycated, which clinicians often use as a longer-window view than a single fasting glucose.

Common units on reports: %

Why people track it over time

People often track A1C across visits because it summarizes a longer period than a one-day glucose reading. Trends can help you notice change before an appointment — they do not, by themselves, diagnose a condition.

Changes over time do not by themselves establish a diagnosis. Learn more

Questions you might ask a healthcare professional

• Ask how this result compares with your prior A1C values and the lab’s reference range on the report.
• Ask whether timing of illness, anemia, or other factors might affect interpretation for you.
• Bring questions about lifestyle context your clinician has already discussed with you — do not self-adjust medications based on this page.