Hemoglobin A1c

Measured in %

An estimate of your average blood sugar over roughly the past 2-3 months, which can read high or low if your red blood cells are unusual.

What it is

HbA1c measures the percentage of your hemoglobin — the oxygen-carrying protein inside red blood cells — that has sugar stuck to it, which reflects roughly the last 2 to 3 months of average blood sugar rather than a single moment. Because it depends on red blood cells living a typical lifespan, conditions that change how long they survive can skew it: some anemias and certain inherited hemoglobin variants can make it read falsely high or falsely low. It's commonly reviewed alongside fasting glucose, and it's an average — so it can't show the ups and downs happening in between.

Typical range

  • Adultsunder 5.7 %

Source · ADA Standards of Care (2026)

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

  • Do I have anything going on with my red blood cells or hemoglobin that could affect how accurate my A1c is?
  • How does my A1c compare with my fasting glucose, and do they tell a consistent story?
  • How often would it make sense for me to recheck this?