A healthy A1C level is below 5.7%. This number represents your average blood sugar over the past two to three months, and it’s one of the most reliable snapshots of how your body handles glucose day to day. 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
When sugar circulates in your bloodstream, some of it attaches to hemoglobin, the protein inside red blood cells that carries oxygen. 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 being replaced, measuring this sugar-coated hemoglobin gives a reliable picture of your blood sugar trends over that window. Unlike a finger-prick glucose test, which captures a single moment, A1C reflects the bigger pattern.
The Three A1C Ranges
The thresholds used by the American Diabetes Association and the CDC break down cleanly:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A result of 5.4% is comfortably healthy. A result of 5.8% isn’t diabetes, but it signals that your blood sugar runs higher than ideal and that lifestyle changes now can prevent progression. Many people sit in the prediabetes range for years without knowing it, because there are no obvious symptoms at this stage.
How A1C Translates to Daily Blood Sugar
A1C percentages can feel abstract. Converting them to estimated average glucose (eAG) makes the number more concrete. The formula is straightforward: multiply your A1C by 28.7, then subtract 46.7. That gives you an average daily blood sugar in mg/dL.
Some practical examples:
- A1C of 5.7%: roughly 117 mg/dL average
- A1C of 6%: about 126 mg/dL
- A1C of 6.5%: about 140 mg/dL
- A1C of 7%: about 154 mg/dL
- A1C of 8%: about 183 mg/dL
- A1C of 9%: about 212 mg/dL
If you already check your blood sugar at home, comparing your daily readings to your A1C-derived average can reveal whether you’re catching the full picture or missing highs and lows.
Targets for People Already Living With Diabetes
Once someone has a diabetes diagnosis, the goal shifts from “normal” to “well controlled.” For most adults with diabetes, the standard target is an A1C of 7% or below. Reaching that level significantly lowers the risk of complications affecting the eyes, kidneys, nerves, and heart.
That target isn’t universal, though. For older adults who are functionally independent and have a life expectancy of more than 10 years, guidelines recommend the same 7% target as younger adults. But for older people with multiple health conditions or who are frail, a range of 7.1% to 8.5% is often more appropriate. Pushing blood sugar too low in these groups raises the risk of dangerous drops in blood sugar, which can cause falls, confusion, and hospitalization. The goal becomes avoiding both the symptoms of high blood sugar and the risks of going too low.
When Results Can Be Misleading
The A1C test assumes your red blood cells have a normal lifespan and behave in typical ways. Several conditions break that assumption and can push your result artificially high or low.
Iron deficiency anemia tends to inflate A1C readings. Because iron-deficient red blood cells live longer than normal, hemoglobin accumulates more sugar coating than it should relative to actual blood sugar levels. This means you could get a prediabetes-range result even if your blood sugar is genuinely normal.
Conditions that shorten red blood cell lifespan do the opposite. Hemolytic anemia, significant blood loss, or recovery from a major bleed can all produce falsely low A1C readings, since the hemoglobin hasn’t been around long enough to accumulate sugar.
Sickle cell trait and other hemoglobin variants can interfere with the test in either direction, depending on the lab method used. Chronic kidney disease complicates things further. Patients on dialysis often see A1C underestimate their true blood sugar, making an alternative test called glycated albumin a more reliable option in that setting.
If you have any of these conditions, your doctor may rely on additional blood sugar tests rather than A1C alone.
How Often to Get Tested
If your blood sugar is well controlled and your treatment plan is stable, testing every six months is sufficient. If your levels are above target, or if you’ve recently changed medications, diet, or exercise habits, every three months makes more sense. That three-month interval lines up naturally with the lifespan of red blood cells, so each test gives you a fully refreshed picture.
For people without diabetes, A1C is typically checked as part of routine bloodwork during annual physicals, especially after age 35 or if risk factors like obesity, family history, or a sedentary lifestyle are present.
What Moves A1C in the Right Direction
Small, sustained changes in daily habits are what shift A1C over time. Because the test reflects a two-to-three-month average, a single great week won’t move the needle, but consistent adjustments will.
Reducing refined carbohydrates and added sugars has the most direct impact on blood sugar levels. Regular physical activity, even moderate walking after meals, helps your muscles pull glucose from the bloodstream more efficiently. Losing 5% to 7% of body weight, if you’re carrying extra, has been shown to cut the risk of progressing from prediabetes to diabetes roughly in half. Sleep matters too: consistently getting fewer than six hours per night impairs the body’s ability to regulate blood sugar.
If you’re in the prediabetes range, the encouraging reality is that this stage is highly reversible. Many people bring their A1C back below 5.7% through diet and exercise alone, without ever needing medication. The key is acting on the number rather than waiting for symptoms that may never come.