Lab test glossary · Blood sugar
Hemoglobin A1c: what it means
Also known as: A1c, HbA1c, glycated hemoglobin
A1c estimates your average blood sugar over the past ~3 months and is the standard test for screening and monitoring diabetes.
What it measures
Hemoglobin A1c measures the percentage of your hemoglobin that has glucose attached to it. Because red blood cells live about three months, A1c reflects your average blood sugar over that window rather than a single moment — which makes it less sensitive to whether you fasted before the draw.
Typical range
Commonly, below 5.7% is considered normal, 5.7–6.4% is the prediabetes range, and 6.5% or higher on two tests supports a diabetes diagnosis — but these thresholds are your clinician's to apply, and conditions affecting red blood cells can skew A1c.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Prediabetes or diabetes
- Rising average blood sugar over recent months
- Some anemias and conditions that lengthen red-cell lifespan can falsely raise it
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Conditions that shorten red-cell lifespan (e.g. hemolytic anemia) can falsely lower it
- Recent significant blood loss or transfusion
Why the trend matters
A1c is most powerful as a trend: watching it drift up or down over years shows whether lifestyle changes or treatment are working, and catches a slow slide toward prediabetes early.
When to talk to your doctor
Any A1c in the prediabetes range or above deserves a conversation with your doctor about next steps; so does an A1c that's rising over successive tests even within the normal range.
Frequently asked questions
What is a normal A1c level?
Below 5.7% is generally considered normal, 5.7–6.4% is the prediabetes range, and 6.5% or higher on two tests supports a diabetes diagnosis — but these thresholds are your clinician's to apply.
How can I lower my A1c?
Because A1c reflects roughly three months of average blood sugar, changes in diet, activity, weight, and (where prescribed) medication move it over months rather than days. Your doctor can set a target and a plan that fit you.
What is the difference between A1c and glucose?
Glucose is your blood sugar at a single moment and depends on whether you fasted; A1c estimates your average over about three months, so it's far less affected by a single meal.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.