A normal A1C level is below 5.7%. This percentage reflects your average blood sugar over the past two to three months, making it one of the most useful snapshots of long-term glucose control. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher on two separate tests indicates diabetes.
What the A1C Test Actually Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more glucose circulating in your blood, the more hemoglobin gets coated. An A1C test measures the percentage of your red blood cells carrying this glucose coating.
The reason the test captures a two- to three-month window is straightforward: red blood cells live about three months. Once glucose attaches to hemoglobin, it stays there for the life of that cell. So your A1C result is essentially a weighted average of your blood sugar over the entire lifespan of your current red blood cells, with more recent weeks influencing the number slightly more than earlier ones.
This makes A1C fundamentally different from a finger-stick glucose reading, which only tells you what your blood sugar is at that exact moment. You could have a perfect fasting glucose reading on the morning of your lab work but still have an elevated A1C if your blood sugar has been running high after meals or overnight for weeks.
The Three A1C Categories
Normal: below 5.7%. Your body is managing blood sugar effectively. Most people in this range don’t need follow-up testing for several years unless they have risk factors like a family history of diabetes, obesity, or a history of gestational diabetes.
Prediabetes: 5.7% to 6.4%. About 98 million American adults fall into this range, and most don’t know it. Prediabetes means your blood sugar is higher than it should be but hasn’t crossed the threshold for a diabetes diagnosis. The good news is that lifestyle changes at this stage, particularly modest weight loss and regular physical activity, can bring your A1C back into the normal range and significantly reduce the risk of progressing to type 2 diabetes.
Diabetes: 6.5% or higher. A single result at or above 6.5% is typically confirmed with a second test before a formal diagnosis is made, unless you’re already showing classic symptoms like excessive thirst, frequent urination, and unexplained weight loss.
What Your A1C Means in Everyday Blood Sugar
Percentages can feel abstract. A more intuitive way to think about A1C is through estimated average glucose (eAG), which translates your result into the kind of number you’d see on a glucose meter. A 5.0% A1C corresponds to an average blood sugar of roughly 97 mg/dL. At 5.7%, you’re averaging about 117 mg/dL. At 6.5%, that average climbs to around 140 mg/dL. And an A1C of 7.0%, which is the general treatment target the American Diabetes Association recommends for most nonpregnant adults with diabetes, translates to an average of 154 mg/dL.
These conversions aren’t perfect for every individual, since the relationship between A1C and average glucose can vary slightly from person to person. But they give you a practical sense of where your blood sugar has been sitting day to day.
A1C Targets for Older Adults
The standard 7.0% target doesn’t apply equally to everyone. For older adults, especially those managing multiple health conditions, clinical guidelines from the American Diabetes Association set different goals based on overall health status.
Older adults who are generally healthy with intact cognitive and physical function typically aim for an A1C below 7.0% to 7.5%. Those managing multiple chronic conditions or experiencing mild to moderate cognitive decline have a more relaxed target of below 8.0%. For people in poor health, with advanced complications, or significant cognitive impairment, the focus shifts away from hitting a specific A1C number entirely. Instead, the priority becomes avoiding dangerously low blood sugar (hypoglycemia) and preventing symptoms of very high blood sugar.
The reasoning behind these looser targets is practical. Older adults face a higher risk of hypoglycemia due to factors like irregular eating patterns, declining kidney function, and certain medications. Severe low blood sugar episodes in older adults are linked to falls, hospitalizations, and even an increased risk of dementia. Pushing for an aggressively low A1C in someone who is frail or cognitively impaired can cause more harm than the slightly elevated blood sugar would.
When A1C Results Can Be Misleading
The A1C test is reliable for most people, but several conditions can skew results in either direction. The CDC identifies the following factors that can falsely raise or lower your A1C:
- Severe anemia and other conditions that affect red blood cell turnover
- Blood disorders like sickle cell anemia or thalassemia, which alter the structure of hemoglobin itself
- Kidney failure or liver disease
- Recent blood loss or transfusions, which change the age distribution of your red blood cells
- Certain medications, including opioids and some HIV treatments
- Pregnancy, particularly early or late stages
If any of these apply to you, your doctor may use alternative tests to assess blood sugar control, such as a fructosamine test (which measures a shorter window of about two to three weeks) or direct glucose monitoring. People of African, Mediterranean, or Southeast Asian descent have higher rates of hemoglobin variants that can interfere with some A1C testing methods, so it’s worth flagging your background if you’ve never been tested before.
How Often to Get Tested
If your A1C is normal and you have no risk factors, testing every three years is generally sufficient. With prediabetes, annual testing helps track whether lifestyle changes are working or whether you’re trending toward diabetes. For people with diabetes, the standard recommendation is testing every three to six months, depending on how stable your blood sugar management is. If your treatment plan has recently changed or your A1C is above your target, testing every three months gives you and your doctor a faster feedback loop to see whether adjustments are helping.
Because the test reflects a rolling average, testing more often than every three months doesn’t add much useful information. Your red blood cells need time to turn over before a new result will meaningfully differ from the last one.