An A1C between 5.7% and 6.4% is the prediabetes range. Below 5.7% is considered normal, and 6.5% or higher meets the threshold for type 2 diabetes. This single blood test gives you a snapshot of your average blood sugar over the past two to three months, making it one of the most common ways prediabetes is identified.
How the A1C Test Works
A1C measures the percentage of hemoglobin in your red blood cells that has glucose attached to it. Hemoglobin is the protein that carries oxygen through your bloodstream, and glucose naturally sticks to it over time. The higher your blood sugar has been, the more glucose accumulates on your hemoglobin. Because red blood cells live for roughly 100 to 120 days, the test captures your average blood sugar levels over that window rather than a single moment in time.
This is what makes A1C different from a finger-stick glucose reading. A fasting glucose test tells you what your blood sugar is right now, which can swing based on what you ate last night or how well you slept. A1C smooths out those day-to-day fluctuations and gives a broader picture.
What the Numbers Mean in Everyday Terms
An A1C percentage translates to an estimated average glucose (eAG) using a standard formula. At 5.7%, the low end of prediabetes, your average blood sugar is running around 117 mg/dL. At 6.0%, it’s roughly 126 mg/dL. At 6.4%, the top of the prediabetes range, your average sits near 137 mg/dL. For context, a healthy fasting blood sugar is below 100 mg/dL, so even a 5.7% A1C signals that your body is starting to handle glucose less efficiently than it should.
Other Tests That Diagnose Prediabetes
A1C isn’t the only diagnostic tool. Two other blood tests can also identify prediabetes, and your doctor may use them alongside or instead of A1C depending on your situation.
- Fasting plasma glucose (FPG): A reading of 100 to 125 mg/dL after an overnight fast falls in the prediabetes range. Below 100 is normal, and 126 or above indicates diabetes.
- Oral glucose tolerance test (OGTT): You drink a sugary solution, then have your blood drawn two hours later. A result of 140 to 199 mg/dL at that two-hour mark signals prediabetes. At 200 or above, it’s diabetes.
These tests sometimes disagree with each other. You might have a normal A1C but a prediabetic fasting glucose, or vice versa. That’s because each test measures a slightly different aspect of blood sugar regulation. When results are borderline or conflicting, repeating the test or running a second type of test helps confirm the diagnosis.
When A1C Results Can Be Misleading
Certain health conditions affect how long your red blood cells survive or how hemoglobin behaves, which can throw off A1C readings. Severe anemia, kidney failure, liver disease, and blood disorders like sickle cell anemia or thalassemia can all push your result falsely high or low. Blood transfusions, significant blood loss, opioids, some HIV medications, and pregnancy (particularly early or late stages) can also skew results.
If any of these apply to you, your A1C may not accurately reflect your true average blood sugar. In those cases, fasting glucose or an oral glucose tolerance test is a more reliable option. This is worth flagging with your provider, especially if your A1C result doesn’t match how you feel or what your home glucose readings show.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends prediabetes and type 2 diabetes screening for adults aged 35 to 70 who are overweight or obese. That starting age was recently lowered from 40 to 35. If your initial result comes back normal, retesting every three years is generally reasonable. If your result lands in the prediabetes range, your provider will likely want to check more frequently to track whether your levels are stable, improving, or climbing toward diabetes.
People with additional risk factors, such as a family history of type 2 diabetes, a history of gestational diabetes, or belonging to a racial or ethnic group with higher diabetes prevalence, may benefit from screening earlier or more often.
The Risk of Progressing to Type 2 Diabetes
Prediabetes is not a guarantee that you’ll develop diabetes, but it is a serious warning signal. Roughly 5 to 10% of people with prediabetes progress to type 2 diabetes each year. Over a decade, a large pooled analysis of 19 cohort studies found that about 12.5% of people with prediabetes had progressed to diabetes. The risk climbs with higher A1C levels within the prediabetes range: someone sitting at 6.3% faces a steeper trajectory than someone at 5.7%.
The flip side is encouraging. Many people with prediabetes return to normal blood sugar levels, particularly with lifestyle changes. Prediabetes is the stage where intervention has the most impact.
Lowering Your A1C Back to Normal
The most effective strategy for reversing prediabetes comes from the Diabetes Prevention Program, a structured approach that focuses on two core goals: losing at least 5 to 7% of your body weight and getting at least 150 minutes of physical activity per week. For someone who weighs 200 pounds, that’s a loss of 10 to 14 pounds. The activity target breaks down to about 30 minutes a day, five days a week, and brisk walking counts.
These aren’t arbitrary numbers. The landmark DPP clinical trial showed that this combination of modest weight loss and regular movement reduced the risk of developing type 2 diabetes by 58% in people with prediabetes. That’s a larger effect than what medication achieved in the same trial.
The changes that move the needle tend to be straightforward: reducing refined carbohydrates and sugary drinks, adding more vegetables and fiber, walking after meals, and improving sleep. None of these require extreme dieting or intense exercise programs. Small, consistent shifts in daily habits are what bring A1C down over time, and you can expect to see changes reflected in your next A1C test within three to six months.