If you have diabetes or are at risk for it, you’ve probably heard of the A1C test. It’s one of the most important tools for diagnosing diabetes and tracking how well blood sugar is controlled over time. Here’s what it measures and what your numbers mean.
What does A1C measure?
When sugar (glucose) circulates in your blood, some of it sticks to hemoglobin, the protein in red blood cells that carries oxygen. The A1C test measures the percentage of hemoglobin that has sugar attached. Because red blood cells live about three months, A1C reflects your average blood sugar over the past two to three months, not just a single moment.
That makes it different from a finger-stick or fasting blood sugar test, which shows your blood sugar at one point in time.
What the numbers mean
According to the CDC:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A diagnosis of diabetes is usually confirmed with a second test. Learn more about prediabetes and how to turn it around.
A1C goals if you have diabetes
For many adults with diabetes, a common goal is an A1C below 7%. But goals are personal. Your doctor may recommend a different target based on your age, other health conditions, risk of low blood sugar and life expectancy. A lower A1C reduces the risk of diabetes complications affecting the eyes, kidneys, nerves and heart.
How often to test
- If your diabetes is well controlled: typically at least twice a year.
- If your treatment changes or you’re not meeting your goal: often every three months.
- If you have prediabetes: usually once a year.
- If your result was normal and you have risk factors: every few years, as your doctor recommends.
What can affect A1C accuracy
Some conditions can make A1C results less accurate, including anemia, recent blood loss or transfusion, certain inherited hemoglobin variants, advanced kidney disease and pregnancy. If your A1C doesn’t match your home glucose readings, your doctor may use other tests.
Ways to lower your A1C
- Build balanced meals with the diabetes plate method.
- Be active most days. Strength training like our resistance band workout helps muscles use glucose.
- Take diabetes medicines as prescribed.
- Lose extra weight if needed.
- Get enough sleep and manage stress.
What this means for you
Know your A1C number and your personal target. Bring your home glucose readings or continuous glucose monitor data to appointments so your doctor can see the full picture. Because A1C is an average, it can hide frequent highs and lows, so daily monitoring is still valuable for many people.
The bottom line
A1C shows your average blood sugar over two to three months. Below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher is diabetes. Working toward your personal A1C goal lowers the risk of complications.
Common questions
Do I need to fast for an A1C test?
No. Because A1C reflects your average over months, you don’t need to fast.
What is estimated average glucose (eAG)?
It’s your A1C converted into the same units as a glucose meter (mg/dL). For example, an A1C of 7% equals an eAG of about 154 mg/dL.
Can stress or illness change my A1C?
A short illness won’t change A1C much, but ongoing high blood sugar from stress, illness or steroid medicines over several weeks can raise it.
Is a continuous glucose monitor better than A1C?
They measure different things. A continuous glucose monitor shows day-to-day patterns, highs and lows, while A1C shows your long-term average. Many people benefit from both.
This article is for general information and isn’t medical advice. Talk with your healthcare provider about your individual needs.
