Your A1C level is a percentage that reflects your average blood sugar over the past two to three months. A normal A1C is below 5.7%, prediabetes falls between 5.7% and 6.4%, and an A1C of 6.5% or higher indicates diabetes. Unlike a finger-stick glucose reading that captures a single moment, A1C gives you and your doctor a longer view of how your body has been handling sugar.
How the A1C Test Works
Hemoglobin is a protein inside red blood cells that carries oxygen through your bloodstream. When sugar circulates in your blood, some of it naturally sticks to hemoglobin. The higher your blood sugar has been, the more sugar-coated hemoglobin you’ll have. An A1C test measures the percentage of your hemoglobin that has sugar attached to it.
The reason the test reflects roughly three months of blood sugar history is straightforward: red blood cells live about three months. Once sugar attaches to a red blood cell’s hemoglobin, it stays there for the life of that cell. So at any given time, your blood contains red blood cells of varying ages, and the sugar coating on all of them collectively tells the story of your recent blood sugar control.
What the Numbers Mean
The A1C result is reported as a percentage. Here’s how those percentages break down:
- Below 5.7%: Normal range. Your blood sugar levels have been healthy.
- 5.7% to 6.4%: Prediabetes. Blood sugar has been higher than normal but not yet in the diabetes range. This is a window where lifestyle changes can make a real difference.
- 6.5% or higher: Diabetes range. A second test is typically done to confirm the diagnosis.
For people already diagnosed with diabetes, the general target is an A1C below 7%, though your specific goal may be higher or lower depending on your age, how long you’ve had diabetes, and other health conditions. Older adults or people at risk for low blood sugar episodes sometimes aim for a slightly higher target to avoid dangerous drops.
A1C Translated to Daily Blood Sugar
A percentage can feel abstract, so it helps to convert A1C into an estimated average glucose (eAG), the number you’d see on a blood sugar meter. The conversion formula is: multiply your A1C by 28.7, then subtract 46.7. That gives you your approximate average blood sugar in mg/dL.
Some common conversions:
- A1C of 6%: average blood sugar around 126 mg/dL
- A1C of 7%: around 154 mg/dL
- A1C of 8%: around 183 mg/dL
- A1C of 9%: around 212 mg/dL
- A1C of 10%: around 240 mg/dL
Keep in mind this is an average. Two people can have the same A1C but very different daily patterns. One person’s blood sugar might stay relatively steady, while another’s swings between highs and lows that happen to average out to the same number. That’s why A1C is best used alongside daily glucose monitoring rather than as a replacement for it.
No Fasting Required
One practical advantage of the A1C test is that you don’t need to fast beforehand. You can eat normally before the blood draw, which makes it easier to schedule than a fasting glucose test. It’s a simple blood draw, and results are usually available within a day or two.
People with diabetes typically get their A1C checked two to four times per year. If your blood sugar is stable and you’re meeting your targets, twice a year is often enough. If your treatment plan recently changed or your levels aren’t where they need to be, testing every three months gives you timely feedback on whether adjustments are working.
When A1C Results Can Be Misleading
Because the test depends on hemoglobin and red blood cells, anything that alters those can throw off your result. Several conditions can make your A1C falsely high or falsely low:
- Severe anemia changes the number and lifespan of red blood cells, which distorts the measurement.
- Kidney failure or liver disease can shift results in either direction.
- Blood disorders like sickle cell anemia or thalassemia produce variant forms of hemoglobin that interfere with standard A1C testing methods.
- Recent blood loss or transfusions replace old red blood cells with new ones, which artificially lowers the reading.
- Certain medications, including some opioids and HIV treatments, can affect accuracy.
- Pregnancy, particularly early or late stages, can also alter results.
If any of these apply to you, your doctor may use a different test to assess blood sugar control, such as a fructosamine test, which measures sugar attached to proteins in your blood over a shorter two-to-three-week window.
What You Can Do With Your Number
If your A1C comes back in the prediabetes range (5.7% to 6.4%), you’re in a position where meaningful change is still very achievable. Losing 5% to 7% of your body weight and getting about 150 minutes of moderate activity per week have been shown to cut the risk of progressing to type 2 diabetes by more than half.
If your A1C is in the diabetes range, each percentage point you lower it reduces your risk of complications affecting your eyes, kidneys, and nerves. Going from 9% to 7%, for example, drops your average blood sugar from roughly 212 mg/dL to 154 mg/dL. That’s a meaningful reduction in the amount of sugar your blood vessels and organs are exposed to every day.
If your A1C is normal, it’s still worth knowing your number, especially if you have risk factors like a family history of diabetes, a sedentary lifestyle, or a higher body weight. Tracking it over time lets you spot a trend toward prediabetes years before symptoms appear, when it’s easiest to reverse course.