A good A1C level is below 5.7%, which is considered normal and means your average blood sugar over the past three months has been in a healthy range. If you already have diabetes, the target shifts: most adults with diabetes should aim for an A1C below 7%, though your ideal number depends on your age, overall health, and risk of low blood sugar episodes.
How the A1C Test Works
A1C measures the percentage of hemoglobin in your red blood cells that has glucose attached to it. Hemoglobin is the protein that carries oxygen through your blood, and glucose naturally sticks to it. The higher your blood sugar runs day to day, the more glucose-coated hemoglobin you’ll have.
Because red blood cells live about three months, an A1C reading captures your average blood sugar over that entire window. That makes it more useful than a single finger-stick glucose reading, which only tells you what’s happening right now. A fasting glucose test might look fine on the morning you happen to eat well, while A1C reveals the bigger picture.
The Three A1C Ranges
Diagnostic thresholds, established by the National Institute of Diabetes and Digestive and Kidney Diseases, break down into three categories:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A result in the prediabetes range means your blood sugar is higher than normal but not yet at the diabetes threshold. This is the window where lifestyle changes, like regular exercise and dietary shifts, can often prevent or delay progression to type 2 diabetes. A diagnosis of diabetes from an A1C test requires confirmation with a second test, unless you already have obvious symptoms like excessive thirst, frequent urination, or unexplained weight loss.
What A1C Means in Everyday Blood Sugar
A1C percentages can feel abstract. Translating them into estimated average glucose (eAG) gives you a number you can compare to the readings on a home glucose meter. The conversion formula is: A1C × 28.7 − 46.7 = eAG in mg/dL.
Here’s what some common A1C values look like in daily terms:
- 6% A1C: roughly 126 mg/dL average
- 7% A1C: roughly 154 mg/dL average
- 8% A1C: roughly 183 mg/dL average
- 9% A1C: roughly 212 mg/dL average
- 10% A1C: roughly 240 mg/dL average
So moving from an A1C of 8% down to 7% means your blood sugar is averaging about 30 mg/dL lower throughout the day. That kind of reduction meaningfully lowers your risk of damage to your eyes, kidneys, and nerves over time.
Targets If You Have Diabetes
The American Diabetes Association recommends most adults with diabetes aim for an A1C below 7%. But “good” doesn’t mean the same number for everyone. Your target may be set higher or lower depending on several factors.
If you’re otherwise healthy, functionally independent, and expect to live many more years, a target below 7% (or even below 6.5%) makes sense because you’ll benefit from preventing long-term complications. For someone younger or recently diagnosed, tighter control pays off over decades.
For older adults or people managing multiple chronic conditions, the goal loosens. The ADA’s framework for older adults suggests these adjusted targets:
- Healthy older adults (few other conditions, good cognitive function): below 7.5%
- Complex health (multiple chronic conditions or mild cognitive impairment): below 8%
- Poor health or limited life expectancy (nursing home residence, advanced illness): below 8.5%
The logic behind these higher targets is practical. Pushing A1C very low requires aggressive treatment, which raises the risk of hypoglycemia, falls, and medication side effects. For someone whose life expectancy is limited, the long-term benefits of tight control may never materialize, while the short-term risks are real and immediate.
Targets During Pregnancy
Pregnancy calls for tighter blood sugar control than usual. Most guidelines recommend an A1C of 6.5% or lower before becoming pregnant, and below 6% during pregnancy. Higher levels increase the risk of complications for both the mother and baby, including birth defects, preterm delivery, and excessive birth weight.
When A1C Results Can Be Misleading
Certain conditions affect how long red blood cells survive or how hemoglobin behaves, which can throw off A1C accuracy. Iron-deficiency anemia, sickle cell trait, and other hemoglobin variants (types S, C, D, and E) are the most common culprits. These can push your result falsely high or falsely low.
A falsely high result might lead to unnecessary treatment. A falsely low result is potentially more dangerous because it can mask poorly controlled blood sugar. If you have a known hemoglobin variant or a blood disorder, your provider may use alternative tests, like fructosamine, to get a more accurate picture.
Heavy bleeding, recent blood transfusions, kidney disease, and liver disease can also skew results. Elevated fetal hemoglobin, which sometimes occurs in adults with leukemia or certain anemias, is another less common source of error.
How Often to Test
If you have diabetes and your blood sugar is well controlled and stable, testing every six months is generally sufficient. If your treatment has recently changed or you’re not meeting your goals, testing every three months gives you faster feedback on whether adjustments are working.
For people without diabetes, A1C testing is part of routine screening, typically starting at age 35 or earlier if you have risk factors like obesity, a family history of diabetes, or a history of gestational diabetes. Your provider will determine the right screening interval based on your risk profile.