A normal hemoglobin A1c is below 5.7%. This number represents your average blood sugar over roughly the past two to three months, giving a broader picture than a single blood sugar reading taken at one moment in time. Results between 5.7% and 6.4% fall into the prediabetes range, and 6.5% or higher 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. This process happens continuously, and the higher your blood sugar runs, the more glucose attaches. Because red blood cells live for about 90 to 120 days, the amount of glucose bound to your hemoglobin reflects your average blood sugar levels over that entire lifespan. When your red blood cells eventually die off and get replaced, the cycle starts fresh.
This is why the test captures a rolling average rather than a snapshot. A fasting blood sugar test tells you what’s happening right now. An A1c tells you what’s been happening for months.
A1c Ranges and What They Mean
The three diagnostic categories are straightforward:
- Below 5.7%: Normal. Your blood sugar regulation is working well.
- 5.7% to 6.4%: Prediabetes. Blood sugar is higher than ideal, and the risk of developing type 2 diabetes is elevated.
- 6.5% or above: Diabetes. A second test is needed to confirm the diagnosis unless symptoms are already present.
You can translate these percentages into average blood sugar using a simple formula: multiply the A1c by 28.7, then subtract 46.7. That gives you estimated average glucose in mg/dL. So a 5.7% A1c corresponds to an average blood sugar of about 117 mg/dL, while a 6.5% A1c translates to roughly 140 mg/dL.
When and How Often to Get Tested
The American Diabetes Association recommends that most adults begin screening at age 35. Earlier testing makes sense if you have risk factors like obesity, a family history of diabetes, a sedentary lifestyle, or a history of gestational diabetes. If your results come back normal, retesting every three years is generally sufficient. Your doctor may suggest more frequent checks if your result lands in the upper end of normal or if your risk profile changes, for instance after significant weight gain.
People already diagnosed with diabetes typically get A1c tests two to four times a year, depending on how stable their blood sugar control is.
Conditions That Can Skew Results
The A1c test assumes your red blood cells have a typical lifespan. Anything that changes how long red blood cells survive can throw off the reading. Conditions that shorten red blood cell life, like hemolytic anemia or recovery from significant blood loss, will make your A1c appear falsely low because the cells haven’t been around long enough to accumulate glucose.
Iron deficiency anemia works in the opposite direction, artificially raising A1c levels. This is especially relevant during late pregnancy, when iron deficiency is common and can push A1c readings higher even in women without diabetes.
Hemoglobin variants, including sickle cell trait and hemoglobin C trait, can also interfere with accuracy depending on the lab method used. People with kidney failure face a similar issue: a chemically altered form of hemoglobin can distort results, and for dialysis patients, A1c often underestimates actual blood sugar levels. If you have any of these conditions, your doctor may rely on alternative markers or interpret your A1c with extra caution.
A1c Targets During Pregnancy
Pregnancy changes the picture considerably. For women with preexisting diabetes, the goal during the first trimester is an A1c below 7%, ideally as close to 6% as possible. By the second and third trimesters, the target tightens to below 6%. These stricter targets exist because elevated blood sugar during pregnancy increases the risk of complications for both mother and baby.
Gestational diabetes, which develops around weeks 24 to 28 of pregnancy, is typically diagnosed with a glucose tolerance test rather than an A1c. This is partly because the red blood cell changes and iron shifts of pregnancy make A1c less reliable as a screening tool during that window.
How Targets Differ for Older Adults
For people already managing diabetes, a “good” A1c isn’t always the same number. Older adults who are otherwise healthy generally aim for an A1c below 7% to 7.5%. But for those dealing with multiple chronic conditions, cognitive decline, or difficulty managing daily activities, the target loosens to below 8%. The reason is practical: pushing blood sugar too low in a frail or cognitively impaired person raises the risk of dangerous hypoglycemia, which can cause falls, confusion, and hospitalization.
For older adults in very poor health or with severe cognitive impairment, clinicians often step away from A1c targets entirely. The priority shifts to simply preventing blood sugar swings that cause symptoms, whether dangerously high or dangerously low.
What a Prediabetes Result Means in Practice
Landing in the 5.7% to 6.4% range is not a diabetes diagnosis, but it is a clear signal. Roughly 70% of people with prediabetes eventually develop type 2 diabetes if nothing changes. The encouraging flip side is that lifestyle changes at this stage are remarkably effective. Losing 5% to 7% of body weight and getting about 150 minutes of moderate physical activity per week has been shown to cut the risk of progressing to diabetes by more than half.
If your A1c comes back in the prediabetes range, retesting in one to two years (rather than the standard three) helps track whether your numbers are stable, improving, or trending upward. Small shifts of even 0.1% to 0.2% over time can indicate a meaningful change in how your body handles blood sugar.