A normal A1C is below 5.7%. This percentage reflects your average blood sugar over roughly the past three months, making it one of the most useful snapshots of long-term blood sugar control. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes.
What the A1C Test Measures
Glucose in your bloodstream naturally attaches to hemoglobin, the protein inside red blood cells that carries oxygen. Once glucose binds to hemoglobin, it stays attached for the life of that red blood cell, which is about 120 days. The A1C test measures the percentage of your hemoglobin that has glucose stuck to it. A higher percentage means more sugar has been circulating in your blood over the past two to three months.
This is what makes A1C different from a finger-stick glucose reading. A single blood sugar check only tells you what’s happening right now. Your A1C captures the bigger picture, smoothing out the daily spikes and dips into one number.
A1C Ranges and What They Mean
The CDC uses three categories:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
These thresholds apply to adults who aren’t pregnant. A result of 5.6% and a result of 4.8% are both considered normal, though lower numbers within that range generally reflect tighter blood sugar control.
If your result comes back in the prediabetes range, it means your blood sugar has been running higher than ideal but hasn’t crossed the diabetes threshold. This is the window where lifestyle changes (more physical activity, dietary shifts, modest weight loss) are most effective at preventing or delaying type 2 diabetes.
How A1C Translates to Daily Blood Sugar
Your A1C corresponds to an estimated average glucose, or eAG, which puts the percentage into the same units you’d see on a home glucose meter. Here’s how common A1C levels map to average blood sugar in mg/dL:
- 5% A1C: ~97 mg/dL
- 6% A1C: ~126 mg/dL
- 7% A1C: ~154 mg/dL
- 8% A1C: ~183 mg/dL
- 9% A1C: ~212 mg/dL
- 10% A1C: ~240 mg/dL
So a normal A1C of 5% means your blood sugar has averaged around 97 mg/dL over the past few months. Each 1% increase in A1C corresponds to roughly a 29 mg/dL jump in average blood sugar. These are averages, though. Two people with the same A1C can have very different day-to-day glucose patterns.
Targets for Children and Teens
The diagnostic cutoffs for prediabetes and diabetes are the same for children as for adults. But for kids already managing diabetes, the treatment targets are slightly more relaxed than what most adults aim for, because tight blood sugar control carries a higher risk of dangerous lows in younger children.
The American Diabetes Association sets age-based A1C goals for children with diabetes:
- Ages 0 to 6: under 8.5% (but above 7.5%)
- Ages 6 to 12: under 8%
- Ages 13 to 19: under 7.5%
These wider targets exist because young children often can’t recognize or communicate when their blood sugar drops too low, and severe hypoglycemia can be especially harmful to developing brains.
Targets for Older Adults
For adults over 65 with diabetes, the goal isn’t always to push A1C as low as possible. Older adults face a higher risk of hypoglycemia, and the body’s ability to recognize and recover from low blood sugar declines with age. Falls triggered by a low blood sugar episode can be serious.
The American Diabetes Association recommends stratifying targets by overall health status. A healthy older adult with few other medical conditions may aim for an A1C below 7.5%. Someone managing multiple chronic illnesses or mild cognitive impairment has a suggested target below 8%. For those in long-term care or with significant cognitive decline, the target relaxes to below 8.5%, because the risks of aggressive blood sugar lowering outweigh the long-term benefits.
The American College of Physicians goes further, advising against targeting a specific A1C number at all in patients over 80 or those with a life expectancy under 10 years due to advanced illness. In those cases, the focus shifts to simply avoiding symptoms of high blood sugar rather than hitting a numerical target.
When A1C Results Can Be Misleading
Because the test depends on red blood cells lasting their full 120-day lifespan, anything that changes how long your red blood cells survive can throw off the result.
Conditions that shorten red blood cell life, like hemolytic anemia or recent significant blood loss, will make your A1C appear falsely low. Your red blood cells haven’t been around long enough to accumulate glucose at a rate that reflects your true average. Conversely, iron deficiency anemia tends to push A1C results falsely high.
Hemoglobin variants, which are more common in people of African, Mediterranean, or Southeast Asian descent, can also interfere. Sickle cell trait, hemoglobin C trait, and elevated fetal hemoglobin can all affect accuracy depending on the lab method used. People with sickle cell disease face compounding issues: anemia, faster red blood cell turnover, and frequent transfusions all make A1C unreliable as a marker of blood sugar control.
Kidney failure creates another problem. A chemical modification of hemoglobin that occurs in advanced kidney disease can skew results, and research suggests A1C tends to underestimate blood sugar in dialysis patients. For these individuals, alternative tests that measure glucose attached to different blood proteins may give a more accurate picture.
If you have any of these conditions, your result still has value, but it needs to be interpreted alongside other measures like home glucose monitoring or continuous glucose data.
How Often to Get Tested
If you don’t have diabetes and your A1C is in the normal range, routine screening typically starts at age 35 or earlier if you have risk factors like obesity, a family history of diabetes, or a history of gestational diabetes. For people already diagnosed with diabetes or prediabetes, the American Diabetes Association recommends testing every six months if your A1C has been at your goal. If your treatment has recently changed or your numbers aren’t where they need to be, testing every three months gives you faster feedback on whether adjustments are working.
The test itself is a simple blood draw. Unlike fasting glucose tests, you don’t need to skip meals beforehand, which makes it convenient for routine checkups.