A normal A1C is below 5.7%. This percentage reflects your average blood sugar over the past two to three months, making it one of the most useful screening tools for diabetes and prediabetes. An A1C between 5.7% and 6.4% falls in the prediabetes range, and 6.5% or higher indicates diabetes.
What the A1C Ranges Mean
The three diagnostic categories are straightforward:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
These thresholds correspond to fasting blood sugar levels you may have seen on other lab work. A fasting glucose of 126 mg/dL or higher aligns with the diabetes A1C cutoff of 6.5%. But the two tests don’t always agree perfectly for the same person, which is why a diagnosis typically requires a second confirmatory test, either a repeat A1C or a different glucose test.
The American Diabetes Association updated its guidance in 2024 to place A1C at the top of the testing hierarchy for diagnosing diabetes and prediabetes, reflecting how widely it’s used in everyday clinical practice.
How the A1C Test Works
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar in your blood over time, the more hemoglobin gets coated. The A1C test measures what percentage of your hemoglobin has glucose attached to it.
Because red blood cells live for roughly three months, the test captures a rolling average rather than a single snapshot. That said, the average isn’t weighted evenly. The 30 days right before your blood draw contribute about 50% of the result, while the period from 90 to 120 days back accounts for only about 10%. So recent blood sugar changes show up more strongly than older ones.
Translating A1C Into Daily Blood Sugar
The percentage on your lab report can feel abstract. A useful conversion exists: multiply your A1C by 28.7, then subtract 46.7. The result is your estimated average glucose (eAG) in mg/dL. Here are some common reference points:
- A1C of 5.7%: roughly 117 mg/dL average
- 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
If you check your blood sugar at home with a finger stick, these numbers give you a bridge between what you see day to day and what your A1C report says about the bigger picture.
Why Your Target Might Differ From “Normal”
If you’ve already been diagnosed with diabetes, your doctor likely isn’t aiming for below 5.7%. The typical management target for most adults with diabetes is an A1C of 7% or lower, but this is personalized based on several factors: your age, whether you take insulin or other medications that can cause low blood sugar, how long you’ve had diabetes, and your overall health.
Someone who is younger, recently diagnosed, and otherwise healthy may be given a tighter target closer to 6.5%. An older adult who has experienced episodes of dangerously low blood sugar, or who has other serious health conditions, may have a more relaxed goal of 7.5% or even 8%. Pushing too aggressively for a low number increases the risk of hypoglycemia, which can be more immediately dangerous than a slightly elevated A1C. For people nearing end of life, A1C testing may not be recommended at all, with the focus shifting entirely to avoiding symptoms.
When the Test Can Be Inaccurate
Certain conditions interfere with A1C results, sometimes significantly. Anything that changes how long your red blood cells survive will throw off the reading. If red blood cells are being destroyed or lost faster than usual (from hemolytic anemia or recovery from major blood loss, for example), your A1C will read falsely low because the hemoglobin hasn’t had as much time to accumulate glucose.
Iron deficiency anemia pushes results in the opposite direction, producing a falsely high A1C. This is especially relevant during late pregnancy, when iron deficiency is common. Nondiabetic pregnant individuals can see elevated A1C readings that don’t reflect actual blood sugar problems.
Genetic hemoglobin variants, including sickle cell trait and hemoglobin C trait, can also distort results depending on the lab method used. People with chronic kidney disease face multiple sources of interference: a modified form of hemoglobin created by kidney dysfunction, anemia from the disease itself, and the effects of treatment. In these cases, an alternative test that measures glucose attachment to a different blood protein (albumin) may give a more reliable picture.
If any of these conditions apply to you, your A1C result might not tell the full story. Your doctor may rely more heavily on fasting glucose, an oral glucose tolerance test, or continuous glucose monitoring data instead.
How Often to Get Tested
If your levels are normal and you have no risk factors, A1C testing during routine physicals is generally sufficient. For people with prediabetes, testing once a year helps track whether blood sugar is trending upward or improving with lifestyle changes. If you have diabetes and your blood sugar is well controlled on a stable treatment plan, testing twice a year is standard. When treatment changes or blood sugar isn’t at goal, testing every three months makes sense, since that aligns with the window of time the test actually measures.
One practical detail worth knowing: you don’t need to fast before an A1C test. Unlike a fasting glucose test, your last meal won’t affect the result, which makes it easier to get done during any routine visit.