A normal A1C level is below 5.7%. This number represents the percentage of your red blood cells that have glucose attached to them, and it reflects your average blood sugar over roughly three months. If your result came back and you’re wondering where you fall, the three key thresholds are: below 5.7% is normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher means diabetes.
How the A1C Test Works
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar circulating in your blood, the more hemoglobin gets coated. An A1C test measures what percentage of your hemoglobin has glucose attached to it.
The reason it captures a three-month window is simple: red blood cells live about three months. So the glucose coating on your hemoglobin is essentially a running record of your blood sugar levels over that entire lifespan. A single fasting blood sugar test tells you what’s happening right now. An A1C tells you what’s been happening for the past 8 to 12 weeks.
Normal, Prediabetes, and Diabetes Ranges
The diagnostic cutoffs used by the CDC, the American Diabetes Association, and most clinicians are straightforward:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
These percentages translate to real blood sugar numbers. An A1C of 6% corresponds to an estimated average glucose of about 126 mg/dL. At 7%, that average jumps to 154 mg/dL. At 8%, you’re looking at an average of roughly 183 mg/dL. The formula behind the conversion is: multiply your A1C by 28.7, then subtract 46.7, and you get your estimated average glucose in mg/dL. So if your A1C is 5.5%, your blood sugar has been averaging around 111 mg/dL over the past three months.
A1C Naturally Rises With Age
Even in people without diabetes, A1C tends to creep up as they get older. A study in Diabetes Care found that A1C increases by about 0.01 percentage points per year in nondiabetic adults. That sounds tiny, but it adds up over decades. Among people under 40 without diabetes, A1C values rarely exceeded 5.6% to 6.0%. Among those over 70, the upper range reached 6.2% to 6.6%, even with normal glucose tolerance.
This age-related increase held true even after adjusting for BMI, sex, and fasting glucose levels. It appears to be a natural part of aging rather than a sign of disease. That said, it means a 75-year-old with an A1C of 5.9% isn’t necessarily in the same metabolic situation as a 30-year-old with the same number.
Treatment Targets Vary by Person
If you already have diabetes, “average” isn’t really the goal. Your target A1C depends on your age, overall health, and how aggressively your blood sugar can be managed without causing problems like dangerously low blood sugar (hypoglycemia).
For otherwise healthy adults with diabetes, the general target is below 7.0%. Healthy older adults typically aim for below 7.0% to 7.5%. For older adults managing multiple chronic conditions or mild cognitive impairment, a target below 8.0% is considered reasonable. And for those in poor health with severe comorbidities, clinicians often move away from strict A1C targets altogether and focus instead on avoiding blood sugar extremes, both high and low.
The logic behind these looser targets for older or sicker patients is practical: aggressively lowering blood sugar with medication carries its own risks, especially hypoglycemia, which can cause falls, confusion, and hospitalization. For someone with limited life expectancy or significant frailty, the long-term benefits of tight glucose control don’t outweigh those immediate dangers.
How Often to Get Tested
If you have diabetes and your blood sugar is well controlled, most guidelines recommend testing A1C at least twice a year. If your treatment plan changes or you’re not hitting your target, your doctor will likely test more frequently, sometimes every three months. For people without diabetes, A1C is typically part of routine screening, especially after age 45 or if you have risk factors like obesity or a family history of diabetes.
What Can Throw Off Your Results
A1C is reliable for most people, but certain conditions can make the number misleadingly high or low. Anything that affects red blood cell turnover will skew results. If your red blood cells are dying faster than normal (as in some types of anemia or sickle cell trait), A1C may read artificially low because the hemoglobin hasn’t been exposed to glucose for the usual three months. Heavy blood loss or recent blood transfusions can have a similar effect.
On the other hand, iron deficiency anemia can push A1C higher than your actual blood sugar would suggest, because red blood cells live longer when iron is scarce. Pregnancy changes red blood cell dynamics too, which is why A1C isn’t the preferred screening tool for gestational diabetes. If you have any of these conditions, your doctor may rely on other glucose tests, like fasting blood sugar or an oral glucose tolerance test, to get a more accurate picture.
What Your A1C Number Actually Means Day to Day
The most practical thing about A1C is the estimated average glucose it represents. Here’s what the common A1C values look like in everyday blood sugar terms:
- A1C 5.0%: ~97 mg/dL average
- A1C 5.7%: ~117 mg/dL average
- A1C 6.5%: ~140 mg/dL average
- A1C 7.0%: ~154 mg/dL average
- A1C 8.0%: ~183 mg/dL average
- A1C 9.0%: ~212 mg/dL average
- A1C 10.0%: ~240 mg/dL average
One important caveat: A1C is an average, which means it can mask big swings. Someone whose blood sugar bounces between 60 and 250 mg/dL throughout the day might have the same A1C as someone whose blood sugar holds steady around 154 mg/dL. Both show an A1C of 7%, but their day-to-day experience and health risks look very different. If you’re managing diabetes, A1C gives you the big picture, but it doesn’t replace regular blood sugar monitoring for understanding what’s happening in real time.