A normal A1C level is below 5.7%, which translates to an average blood sugar of roughly 117 mg/dL over the past two to three months. Once A1C reaches 5.7% to 6.4%, it falls into the prediabetes range, and 6.5% or higher is the threshold for a diabetes diagnosis. Understanding where your number falls on this scale, and what it actually measures, helps you make sense of one of the most common blood tests in routine healthcare.
What the A1C Test Measures
The A1C test works by measuring how much sugar has attached to hemoglobin, the protein inside red blood cells that carries oxygen. When blood sugar is elevated, glucose naturally sticks to hemoglobin in a process called glycation. Because red blood cells live for about 90 to 120 days, the amount of sugar coating on your hemoglobin reflects your average blood sugar over roughly the last two to three months rather than a single moment in time.
This makes A1C fundamentally different from a finger-stick glucose reading or a fasting blood sugar test, both of which capture what’s happening right now. A1C gives a longer view, which is why it’s the standard tool for both diagnosing diabetes and tracking how well blood sugar is being managed over time.
Normal, Prediabetes, and Diabetes Ranges
The American Diabetes Association defines three categories:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A result in the prediabetes range means your blood sugar is higher than normal but hasn’t crossed the diabetes line. About one in three American adults fall into this category, and many don’t know it because prediabetes rarely causes noticeable symptoms. The good news is that lifestyle changes at this stage, particularly weight loss and regular physical activity, can slow or reverse the progression to type 2 diabetes.
How A1C Translates to Daily Blood Sugar
An A1C percentage can feel abstract. The concept of estimated average glucose (eAG) makes it more concrete by converting your A1C into the kind of mg/dL number you’d see on a glucose meter. The formula is straightforward: multiply your A1C by 28.7, then subtract 46.7.
Here’s what that looks like in practice:
- A1C of 5.7%: roughly 117 mg/dL
- A1C of 6.0%: about 126 mg/dL
- A1C of 6.5%: about 140 mg/dL
- A1C of 7.0%: about 154 mg/dL
- A1C of 8.0%: about 183 mg/dL
- A1C of 9.0%: about 212 mg/dL
- A1C of 10.0%: about 240 mg/dL
If you wear a continuous glucose monitor or test your blood sugar at home, your daily readings will bounce above and below your eAG throughout the day. That’s expected. The A1C captures the overall trend, not the peaks and valleys.
Target Goals for People With Diabetes
If you’ve already been diagnosed with diabetes, the goal isn’t necessarily to get back below 5.7%. For most nonpregnant adults, aiming for an A1C below 7% is the standard target. That number balances meaningful risk reduction against the real danger of pushing blood sugar too low, which can cause dizziness, confusion, and even loss of consciousness.
Research published in Diabetes Care found that the risk of microvascular complications (damage to small blood vessels in the eyes, kidneys, and nerves) increases significantly once A1C rises above 7.2%, while there was no additional benefit to pushing below about 6.7% in patients with serious kidney disease. In other words, lower isn’t always better once you’re in a healthy range.
For older adults or people with other serious health conditions, a less aggressive target of below 8% is often more appropriate. Tight blood sugar control requires more frequent monitoring and carries a higher risk of dangerous lows, which can be especially harmful for people who are frail or live alone. Targets during pregnancy are also different and typically tighter, reflecting the specific risks that elevated blood sugar poses to fetal development.
How Often to Get Tested
If your A1C is within your target range and your treatment plan hasn’t changed, testing every six months is generally sufficient. If your last result was above your goal or you’ve recently started or adjusted medication, every three months gives you and your healthcare team a faster feedback loop to see whether changes are working.
For people without diabetes, A1C is commonly checked as part of routine screening starting at age 35, or earlier if you have risk factors like obesity, a family history of diabetes, or a history of gestational diabetes.
When A1C Results Can Be Misleading
The test is reliable for most people, but certain conditions can skew results in either direction. Anything that changes how long your red blood cells survive or how hemoglobin behaves will affect accuracy.
Conditions that can produce a falsely high or falsely low A1C include:
- Severe anemia: fewer healthy red blood cells distort the measurement
- Kidney failure or liver disease: both can alter red blood cell turnover
- Blood disorders like sickle cell anemia or thalassemia: these change the structure of hemoglobin itself, and some testing methods can’t distinguish normal hemoglobin from variant forms
- Recent blood loss or transfusions: introducing new red blood cells or losing old ones throws off the two-to-three-month average
- Certain medications: some opioids and HIV medications can interfere with results
- Pregnancy: changes in blood volume during early or late pregnancy can affect readings
If any of these apply to you, your provider may use alternative tests like fructosamine (which measures a shorter window of blood sugar control) or rely more heavily on direct glucose monitoring to get an accurate picture.