A normal hemoglobin A1c level is below 5.7%. This single number tells you your average blood sugar over roughly the past two to three months, making it one of the most useful screening tools for prediabetes and type 2 diabetes. An A1c between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes.
What the A1c Test Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar circulating in your blood over time, the more hemoglobin gets coated. Because red blood cells live an average of about 106 days before your body replaces them, the A1c test captures a rolling picture of your blood sugar that spans roughly two to three months. A single fasting glucose reading can swing based on what you ate the night before or how stressed you are that morning. A1c smooths all of that out.
One important detail: more recent weeks weigh more heavily in the result than earlier weeks. If your blood sugar was well controlled two months ago but spiked over the last few weeks, that recent change will tilt your A1c upward more than you might expect.
Normal, Prediabetes, and Diabetes Ranges
The diagnostic cutoffs, based on criteria from the National Institute of Diabetes and Digestive and Kidney Diseases, break down simply:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
If your result comes back normal, your doctor will schedule follow-up testing based on your age and risk factors. A prediabetes result typically means retesting every one to two years. A diabetes diagnosis usually calls for A1c testing at least twice a year, sometimes more depending on your treatment plan.
Translating A1c Into Everyday Blood Sugar
Percentages can feel abstract. A useful conversion formula turns your A1c into an estimated average glucose (eAG) in the same mg/dL units a fingerstick meter displays. The formula is: multiply your A1c by 28.7, then subtract 46.7.
Here’s what that looks like in practice:
- A1c of 5.7% (top of normal): roughly 117 mg/dL average
- A1c of 6.0%: about 126 mg/dL
- A1c of 6.5% (diabetes threshold): 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
These are averages. An A1c of 7% doesn’t mean your blood sugar sits at 154 mg/dL all day. It means your levels swing higher and lower throughout the day, and 154 is roughly the midpoint over two to three months.
Targets Differ by Age and Health
The 5.7% threshold for “normal” applies to diagnosis, meaning the line between no diabetes and prediabetes. But if you already have diabetes, your treatment target is a separate question, and it varies.
For most adults managing type 2 diabetes, the general goal is an A1c below 7%. Healthy older adults are often given a slightly more relaxed target of below 7.5%, because aggressively lowering blood sugar in older people raises the risk of dangerous drops (hypoglycemia) without always providing long-term benefit. Older adults with significant health conditions may aim for below 8%, and those in poor overall health may have targets as high as 8.5%, with the priority being comfort and avoiding severe highs or lows rather than hitting a tight number.
Children and teenagers with type 1 diabetes also have different targets. Toddlers and preschoolers typically aim for below 8.5%, school-age children below 8%, and adolescents below 7.5%. These wider ranges reflect the difficulty of tight glucose control in growing bodies and the particular danger of low blood sugar in young children.
What the Test Gets Right and Wrong
No fasting is required for an A1c test, which makes it more convenient than a fasting glucose test. You can eat normally beforehand. That said, your doctor may order other bloodwork at the same visit (such as cholesterol) that does require fasting, so it’s worth asking ahead of time.
The test is reliable for most people, but several conditions can throw it off. Anything that changes how long your red blood cells survive will skew results. If your red blood cells are destroyed faster than normal, as happens with hemolytic anemia or significant blood loss, your A1c will read falsely low because the hemoglobin has less time to accumulate sugar. Iron deficiency anemia, on the other hand, pushes A1c falsely high. This is especially relevant during late pregnancy, when iron deficiency is common and can inflate A1c readings even in women without diabetes.
Hemoglobin variants, such as sickle cell trait or disease, can also interfere with the test. People with sickle cell disease face a combination of factors (anemia, faster red cell turnover, transfusions) that make A1c unreliable as a long-term blood sugar marker. In these cases, alternative tests that measure sugar attached to other blood proteins, rather than hemoglobin, give a more accurate picture.
Kidney disease creates another wrinkle. In people on dialysis, chemical changes to hemoglobin can distort A1c results, and the test tends to underestimate actual blood sugar levels. For anyone with advanced kidney disease, doctors often rely on different glycemic markers or more frequent glucose monitoring instead.
Who Should Get Tested
The CDC recommends an A1c test for everyone over 45. If you’re younger than 45 but carry excess weight along with any other risk factor for type 2 diabetes (family history, physical inactivity, a history of gestational diabetes, or belonging to a higher-risk ethnic group), testing is also recommended. A prediabetes result doesn’t mean diabetes is inevitable. It means your blood sugar is higher than normal but still in a range where lifestyle changes, particularly losing 5% to 7% of body weight and increasing physical activity, can often bring it back down or prevent progression.
If your result falls in the prediabetes range and you’re wondering how urgently to act: an A1c of 6.0% corresponds to an average blood sugar of about 126 mg/dL, which is meaningfully different from 5.4% (about 108 mg/dL). Both are technically “not diabetes,” but the higher number signals more insulin resistance and a shorter runway before crossing the 6.5% line. The closer you are to that threshold, the more value you’ll get from early intervention.