A normal A1C is below 5.7%. This number represents your average blood sugar over the past two to three months, expressed as a percentage. It’s one of the most common blood tests used to screen for prediabetes and diabetes, and understanding where you fall on the scale can tell you a lot about your metabolic health.
The Three A1C Ranges
The CDC uses three categories to interpret A1C results:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A result of 5.6% is considered normal. A result of 5.7% puts you in the prediabetes range, even though the difference sounds tiny. That cutoff exists because the risk of progressing to type 2 diabetes rises meaningfully once you cross it. Prediabetes doesn’t mean you have diabetes, but it does mean your body is starting to struggle with blood sugar regulation, and lifestyle changes at this stage can often reverse the trend.
What A1C Actually Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more glucose circulating in your blood over time, the more hemoglobin gets coated. Because red blood cells live for roughly two to three months before your body replaces them, measuring the percentage of hemoglobin with glucose attached gives a reliable snapshot of your average blood sugar over that window.
This is why A1C is more useful than a single finger-stick glucose reading. A finger stick tells you what your blood sugar is right now, which can swing based on your last meal, stress, or exercise. A1C smooths all of that out into one number that reflects the bigger picture.
What Your A1C Translates to in Daily Blood Sugar
If you’ve ever checked blood sugar with a glucose meter, you might wonder how a percentage maps onto those familiar mg/dL numbers. There’s a standard formula that converts A1C into an estimated average glucose, or eAG. It works like this: multiply your A1C by 28.7, then subtract 46.7.
Here’s what that looks like in practice:
- A1C of 5.0%: estimated average glucose of about 97 mg/dL
- A1C of 5.7%: about 117 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
These are averages, not exact matches to any single glucose reading you’d see on a meter. But they help you visualize what’s happening in your blood day to day.
A1C Goals Can Differ by Age and Health
The “below 5.7%” threshold defines what’s normal for screening purposes. But if you already have diabetes, the target your doctor sets may be different from someone else’s, especially as you get older.
The American Diabetes Association recommends that older adults who are otherwise healthy aim for an A1C below 7.0% to 7.5%. For older adults managing multiple serious health conditions or significant cognitive or physical limitations, a less aggressive target of below 8.0% is often more appropriate. The reasoning is practical: pushing blood sugar too low with medications carries real risks, including dangerous drops in blood sugar (hypoglycemia) that can cause falls, confusion, or hospitalization. For someone with a complex health picture, avoiding those lows matters more than hitting a tight number.
Conditions That Skew Your Results
A1C is reliable for most people, but certain conditions can make the number misleadingly high or low. Since the test depends on hemoglobin inside red blood cells, anything that changes how long your red blood cells survive or alters hemoglobin itself will affect the result.
Iron deficiency anemia, which is common in women and during pregnancy, tends to push A1C readings higher than your actual average blood sugar. This happens because iron-deficient red blood cells live longer, giving glucose more time to accumulate on hemoglobin. Late pregnancy can raise A1C for the same reason, even in women without diabetes.
Conditions that shorten red blood cell lifespan have the opposite effect. If you have hemolytic anemia, recent significant blood loss, or receive blood transfusions, your A1C may read falsely low because the red blood cells haven’t been around long enough to collect much glucose.
Sickle cell disease and sickle cell trait also complicate A1C testing. The altered hemoglobin in these conditions can interfere with the lab methods used to measure glycation, and the faster turnover of red blood cells adds another layer of inaccuracy. Kidney disease, particularly in people on dialysis, tends to cause A1C to underestimate true blood sugar levels. In these situations, doctors may rely on alternative markers like fructosamine or glycated albumin to get a clearer picture.
How Often to Get Tested
If you’ve never been flagged for blood sugar issues, A1C is typically part of routine bloodwork during a checkup. Once you have a prediabetes or diabetes diagnosis, the testing schedule becomes more specific. The CDC recommends testing every three months if your treatment has recently changed or you’re not meeting blood sugar goals. If things are stable and you’re consistently hitting your targets, every six months is sufficient.
Units Outside the U.S.
If you get lab results in another country, you may see A1C reported in mmol/mol instead of a percentage. This is the international standard unit. A normal A1C of 5.7% converts to about 39 mmol/mol. The diabetes threshold of 6.5% equals about 48 mmol/mol. The conversion formula is: multiply the percentage minus 2.15 by 10.929. Most online calculators will do this instantly if you need to compare results across systems.