A normal hemoglobin A1c level is below 5.7%. This number reflects your average blood sugar over roughly the past two to three months, making it one of the most reliable snapshots of long-term glucose control. 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. The more glucose circulating in your blood, the more hemoglobin gets coated. The A1c test measures the percentage of hemoglobin molecules with glucose attached.
Because red blood cells live about 120 days, the test captures a rolling average of your blood sugar. It’s not weighted equally across that window, though. About half the result reflects the most recent 30 days. Another 40% comes from days 31 through 90, and only about 10% reflects anything beyond 90 days. So a big change in your eating or medication will start showing up in your next A1c, but it won’t fully register until a couple of months have passed.
What Each A1c Range Means
The CDC uses three categories:
- Below 5.7%: Normal. Your blood sugar regulation is working well.
- 5.7% to 6.4%: Prediabetes. Blood sugar is higher than normal but not yet in the diabetes range. This is the window where lifestyle changes can make the biggest difference.
- 6.5% or above: Diabetes. A second test is typically done to confirm the diagnosis.
To put those percentages in concrete terms, each A1c point corresponds to an estimated average glucose level. An A1c of 5% translates to an average blood sugar of roughly 97 mg/dL. At 6%, that average jumps to about 126 mg/dL. At 7%, it’s around 154 mg/dL. The relationship is linear: each 1% increase in A1c adds roughly 29 mg/dL to your estimated average glucose.
Target A1c for People With Diabetes
If you’ve already been diagnosed with diabetes, “normal” isn’t the goal your doctor is aiming for. The American Diabetes Association recommends an A1c below 7% for most nonpregnant adults. That target balances good blood sugar control against the risk of pushing glucose too low, which can cause dangerous drops in blood sugar. Some people may have a tighter or looser target depending on age, other health conditions, and how their body responds to treatment.
A1c During Pregnancy
Pregnancy changes the math. Red blood cell turnover speeds up, which naturally lowers A1c readings in all pregnant people, whether they have diabetes or not. For those with preexisting diabetes, the ideal A1c goal drops to below 6% if it can be reached safely without causing low blood sugar episodes. That target can be relaxed to below 7% when tighter control isn’t practical.
A1c also has a blind spot during pregnancy: it averages glucose over weeks, so it can miss the sharp blood sugar spikes after meals that are particularly harmful to fetal development. For that reason, direct glucose monitoring is the primary tool during pregnancy, with A1c serving as a secondary check.
When A1c Results Can Be Misleading
The test assumes your red blood cells have a typical lifespan. Anything that shortens or lengthens that lifespan throws off the reading. Certain anemias, sickle cell disease, significant kidney disease, and liver failure can all alter how long red blood cells survive, producing A1c results that don’t match your actual blood sugar levels.
Genetic hemoglobin variants also matter. The four most common are hemoglobin S (sickle cell trait), hemoglobin E, hemoglobin C, and hemoglobin D. These variants can cause falsely high or falsely low A1c readings depending on which laboratory method is used to run the test. If your A1c result doesn’t line up with your daily glucose readings or other blood sugar tests, the discrepancy could stem from one of these variants. The National Glycohemoglobin Standardization Program maintains a list of which testing methods are affected by which variants, so your lab can verify whether its method is reliable for your specific situation.
How Often to Get Tested
If you’re being treated for diabetes and haven’t yet reached a stable blood sugar target, testing every three months lets you and your doctor see whether treatment adjustments are working. Once your levels are consistently on target, every six months is sufficient. More frequent testing may be appropriate for children with type 1 diabetes, anyone planning a pregnancy, or people who’ve recently made major changes to their medications or lifestyle.
If you don’t have diabetes, A1c is commonly included as part of routine screening, especially if you have risk factors like a family history of diabetes, a BMI over 25, or an age over 35. A single normal result doesn’t mean you never need to check again, since blood sugar regulation can shift gradually over years.