A normal A1C is below 5.7%. This number represents the percentage of your red blood cells that have glucose stuck to them, and it reflects your average blood sugar over roughly the past two to three months. An A1C between 5.7% and 6.4% falls in the prediabetes range, and 6.5% or higher indicates diabetes.
What A1C Actually Measures
Glucose in your bloodstream naturally attaches to hemoglobin, the protein inside red blood cells that carries oxygen. The higher your blood sugar runs over time, the more hemoglobin gets coated with glucose. Since red blood cells live an average of about 80 days (not the 120 days often cited in older sources), an A1C result is essentially a weighted average of your blood sugar over that lifespan, with more recent weeks counting more heavily. About 50% of the shift toward a new A1C value happens within the first 30 days of a blood sugar change.
This is what makes A1C more useful than a single blood sugar reading. A finger stick or fasting glucose test captures one moment in time. A1C captures the bigger picture.
A1C Ranges at a Glance
- Normal: Below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
To put these numbers in more familiar terms, the American Diabetes Association uses a formula to convert A1C into an estimated average glucose. A 5.7% A1C corresponds to an average blood sugar of about 117 mg/dL. At 6.0%, that average rises to 126 mg/dL. At 6.5%, the diabetes threshold, your blood sugar has been averaging around 140 mg/dL. By the time A1C reaches 8%, average blood sugar is roughly 183 mg/dL, and at 10% it’s around 240 mg/dL.
Target A1C If You Have Diabetes
Normal and target are two different things. If you’ve already been diagnosed with diabetes, the goal isn’t necessarily to get back below 5.7%. The 2025 American Diabetes Association Standards of Care recommend an A1C below 7% for most nonpregnant adults with diabetes. That translates to an average blood sugar of about 154 mg/dL. Some people can safely aim lower, closer to 6.5%, if they can get there without frequent episodes of low blood sugar or other side effects from treatment.
For older adults, targets are often more relaxed. Guidelines from several international bodies generally recommend an A1C of 7% to 7.5% for healthy older adults and 7.5% to 8.5% for those who are frail or managing multiple chronic conditions. The reasoning is straightforward: aggressively lowering blood sugar in these groups increases the risk of dangerous lows without providing enough long-term benefit to justify it. Aging itself tends to raise A1C slightly.
Children and adolescents with diabetes typically share the same under-7% target as adults, though tighter goals (below 6.5%) may be appropriate for some kids, particularly those with type 2 diabetes who have a low risk of hypoglycemia.
How Often to Get Tested
If you’re being treated for diabetes and your blood sugar is well controlled, testing every six months is generally sufficient. If you’re still working toward your target or have recently changed medications or lifestyle habits, every three months is more appropriate. No fasting is required before an A1C test, which makes it simpler than a fasting glucose test. You can eat and drink normally beforehand.
When A1C Results Can Be Misleading
Several conditions can push your A1C reading higher or lower than your actual blood sugar control would suggest. Anything that shortens the lifespan of your red blood cells, such as hemolytic anemia or recovery from significant blood loss, will make your A1C appear falsely low because your red blood cells haven’t been around long enough to accumulate glucose. Iron deficiency anemia, on the other hand, is associated with falsely elevated A1C readings.
Genetic hemoglobin variants, including sickle cell trait and hemoglobin C trait, can also interfere with the accuracy of certain A1C testing methods. Kidney disease adds another layer of complexity: patients on dialysis often have A1C values that underestimate their true blood sugar levels. In these situations, doctors may rely on alternative markers or continuous glucose monitoring to get a clearer picture.
Pregnancy can also affect red blood cell turnover in ways that make A1C less reliable, which is why it’s not the primary tool used to monitor blood sugar during pregnancy.
What a Prediabetes Result Means
If your A1C comes back between 5.7% and 6.4%, you’re in the prediabetes range. This doesn’t mean diabetes is inevitable. It means your blood sugar is running higher than normal and the trend is heading in the wrong direction. The practical value of catching this early is significant: moderate changes in diet, physical activity, and weight (even a 5% to 7% loss of body weight) have been shown to delay or prevent the progression to type 2 diabetes. A prediabetes result is an early warning, not a diagnosis, and it’s one of the most actionable results you can get from a routine blood test.