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HbA1c blood test

Hemoglobin A1c

In short

A typical adult HbA1c result is 4 to 5.6 %. Doctors call 5.7–6.4% (39–47 mmol/mol) the prediabetes range, and 6.5% (48 mmol/mol) or higher the range used for diabetes. These are ranges, not a diagnosis; diabetes is usually confirmed with a second test. Always read your result against the range printed on your own report.

Your average blood sugar over the past two to three months.

Sugar in your blood sticks to hemoglobin, the protein in red blood cells. Those cells live about three months, so A1C shows your average sugar over that time. You don't need to fast for it.

Is my HbA1c high or low?

Type your result to see where it sits.

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Typical range

ForRangeUnit
Adults4–5.6%
Adults20–38mmol/mol

Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.

If your HbA1c is high

Doctors call 5.7–6.4% (39–47 mmol/mol) the prediabetes range, and 6.5% (48 mmol/mol) or higher the range used for diabetes. These are ranges, not a diagnosis; diabetes is usually confirmed with a second test.

Common reasons

  • Low iron, which can make A1C read higher than your true average
  • Older age, as A1C drifts up slowly over the years
  • Steroid medicines and some other medicines
  • Insulin resistance, when the body responds less to insulin, often with weight gain
  • Prediabetes or diabetes
  • Less often: an inherited hemoglobin type that the lab method misreads

If your HbA1c is low

A low A1C is uncommon. It most often means red blood cells are living shorter lives than usual, which makes A1C read low.

Common reasons

  • Recent blood loss or a blood transfusion
  • Pregnancy, when A1C often runs lower
  • Conditions that break down red blood cells faster
  • Less often: an inherited hemoglobin type, advanced kidney disease or liver disease

What can throw it off

Anemia, recent blood loss or a transfusion, pregnancy and some inherited hemoglobin types can make A1C misleading.

Questions to take to your appointment

  1. 1Which range does my A1C fall in, and should we repeat it?
  2. 2Could anemia or my red cells be skewing this result?
  3. 3How does this compare with my earlier A1C results?

Read together with

Doctors rarely read HbA1c alone. These usually sit next to it.

Quick answers

What is the HbA1c blood test?

HbA1c (Hemoglobin A1c): Your average blood sugar over the past two to three months. Sugar in your blood sticks to hemoglobin, the protein in red blood cells. Those cells live about three months, so A1C shows your average sugar over that time. You don't need to fast for it.

What is a normal HbA1c level?

For most adults, HbA1c is typically 4 to 5.6 %. Some countries print it in mmol/mol, so check the unit first. Labs differ a little, so the range printed next to your result is the one to go by.

What does a high HbA1c mean?

Doctors call 5.7–6.4% (39–47 mmol/mol) the prediabetes range, and 6.5% (48 mmol/mol) or higher the range used for diabetes. These are ranges, not a diagnosis; diabetes is usually confirmed with a second test. Common reasons include low iron, which can make A1C read higher than your true average; older age, as A1C drifts up slowly over the years; steroid medicines and some other medicines; and insulin resistance, when the body responds less to insulin, often with weight gain. A doctor reads it together with your other results and how you feel.

What does a low HbA1c mean?

A low A1C is uncommon. It most often means red blood cells are living shorter lives than usual, which makes A1C read low. Common reasons include recent blood loss or a blood transfusion; pregnancy, when A1C often runs lower; conditions that break down red blood cells faster; and less often: an inherited hemoglobin type, advanced kidney disease or liver disease.

What can affect my HbA1c result?

Anemia, recent blood loss or a transfusion, pregnancy and some inherited hemoglobin types can make A1C misleading.

What should I ask my doctor about my HbA1c?

Questions worth taking to the appointment: Which range does my A1C fall in, and should we repeat it? Could anemia or my red cells be skewing this result? How does this compare with my earlier A1C results?

What this page can’t do

It reads each number on its own.

Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.

It doesn't know you.

Your age, your medicines, how you feel and your last result all change what a number means.

It doesn't remember.

Close this page and your results are gone. That's on purpose: nothing was ever sent to us.

We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.

Vita: Health Coach on the App Store

Sources

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