A normal A1C is below 5.7%. This number represents the percentage of your hemoglobin (a protein in red blood cells) that has glucose attached to it, giving you a snapshot of your average blood sugar over the past two to three months. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes.
What A1C Actually Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the oxygen-carrying protein inside red blood cells. The more sugar in your blood over time, the more hemoglobin gets coated. Since red blood cells live for roughly 90 to 120 days before your body replaces them, an A1C test captures a rolling average of your blood sugar across that entire window rather than a single moment in time.
This makes A1C different from a fingerstick glucose reading or a fasting blood sugar test, both of which tell you what’s happening right now. A1C tells you what’s been happening for months. That’s why it’s considered the primary screening and monitoring tool for diabetes, and the American Diabetes Association places it at the top of its testing hierarchy.
The Three A1C Categories
The National Institute of Diabetes and Digestive and Kidney Diseases defines the ranges this way:
- 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 has been running higher than ideal but hasn’t crossed the diabetes threshold. About 1 in 3 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 often bring A1C back below 5.7%.
A result of 6.5% or above on two separate tests is typically enough for a diabetes diagnosis. However, this number alone doesn’t determine your treatment plan. Your age, overall health, and other medical conditions all factor into the A1C target your provider will recommend for you personally.
How A1C Translates to Daily Blood Sugar
If you check blood sugar with a glucose meter, it helps to understand what your A1C means in everyday numbers. The conversion formula is: (28.7 × A1C) − 46.7 = estimated average glucose in mg/dL. Here’s what that looks like in practice:
- A1C of 5.7%: estimated average glucose of about 117 mg/dL
- A1C of 6.0%: estimated average glucose of about 126 mg/dL
- A1C of 7.0%: estimated average glucose of about 154 mg/dL
- A1C of 8.0%: estimated average glucose of about 183 mg/dL
Keep in mind this is an average. Two people with identical A1C results can have very different daily patterns. One might have relatively stable blood sugar hovering near that average, while the other swings between highs and lows that happen to land at the same mean. That’s one reason continuous glucose monitors have become a popular complement to A1C testing.
A1C Targets for People With Diabetes
If you’ve already been diagnosed with diabetes, “normal” shifts from a diagnostic category to a treatment goal, and that goal varies from person to person. For most non-pregnant adults with diabetes, an A1C below 7% is a common target. But this isn’t universal.
Younger, healthier people who were recently diagnosed may aim for something closer to 6.5%, while older adults or those with heart disease, a long history of diabetes, or a high risk of low blood sugar episodes may be given a more relaxed target of 7.5% or even 8%. Research has shown that pushing aggressively toward near-normal A1C levels in people with long-standing type 2 diabetes and cardiovascular risk can sometimes cause more harm than benefit, largely because of dangerous drops in blood sugar.
When A1C Results Can Be Misleading
Several medical conditions can push your A1C reading higher or lower than your actual average blood sugar warrants. Anything that changes how long your red blood cells survive will throw off the measurement, because A1C depends on glucose accumulating on hemoglobin over a cell’s full lifespan.
Conditions that shorten red blood cell life, like hemolytic anemia, recovery from significant blood loss, or sickle cell disease, tend to produce falsely low A1C results. Your red blood cells simply don’t live long enough to collect as much glucose as they otherwise would. On the other end, iron deficiency anemia is associated with falsely high A1C readings. Iron replacement therapy has been shown to lower A1C in both diabetic and non-diabetic individuals, which confirms the reading was inflated to begin with.
Kidney failure adds another layer of complexity. Patients on dialysis often have A1C results that underestimate their true blood sugar levels. Hemoglobin variants, which are more common in people of African, Mediterranean, or Southeast Asian descent, can also interfere with certain A1C testing methods. If you have any of these conditions, your provider may use alternative markers like fructosamine or glycated albumin to get a more accurate picture.
A1C During Pregnancy
Pregnancy changes the equation. Blood volume increases, red blood cell turnover speeds up, and iron demands rise, all of which can affect A1C accuracy. An A1C of 6.5% or higher in early pregnancy suggests pre-existing diabetes, but research has found that using that cutoff alone could miss nearly three-quarters of women who actually have diabetes during pregnancy.
A lower threshold of 5.7% catches more cases and identifies women at increased risk for pregnancy and neonatal complications. For this reason, A1C is often used as one piece of the puzzle during pregnancy rather than the sole diagnostic tool, with oral glucose tolerance testing filling in the gaps.
How Often to Get Tested
If you don’t have diabetes and your results are normal, A1C testing every three years is a reasonable screening schedule starting 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 with prediabetes, annual testing helps track whether blood sugar is trending upward or responding to lifestyle changes.
If you have diabetes and your blood sugar is well controlled on a stable treatment plan, testing twice a year is generally sufficient. When a treatment plan changes or blood sugar isn’t at goal, testing every three months gives you and your provider faster feedback on whether adjustments are working. Since A1C reflects a two-to-three-month window, testing more frequently than that won’t yield meaningful new information.