A1C levels measure the percentage of your red blood cells that have glucose attached to them, giving you a snapshot of your average blood sugar over the past two to three months. A normal A1C is below 5.7%, levels between 5.7% and 6.4% fall in the prediabetes range, and 6.5% or higher indicates diabetes.
What A1C Actually Measures
Hemoglobin is the protein inside red blood cells that carries oxygen. As blood sugar rises, glucose molecules attach to hemoglobin in a process called glycation. The more sugar circulating in your blood, the more hemoglobin gets coated. Since red blood cells live for about three months before your body replaces them, the A1C test captures a rolling average of your blood sugar during that window rather than a single moment in time.
This makes A1C fundamentally different from a finger-prick glucose reading or a fasting blood sugar test. Those tests tell you what’s happening right now. A1C tells you what’s been happening for weeks. That’s why it’s the primary tool for diagnosing diabetes and tracking how well blood sugar is being managed over time.
What the Numbers Mean
The American Diabetes Association uses three A1C ranges for diagnosis:
- Below 5.7%: Normal blood sugar control
- 5.7% to 6.4%: Prediabetes
- 6.5% or higher: Diabetes
These percentages can feel abstract, so it helps to convert them to the kind of blood sugar numbers you’d see on a glucose meter. An A1C of 5% translates to an estimated average glucose of about 97 mg/dL. At 6%, that average climbs to 126 mg/dL. A 7% A1C means your blood sugar has been averaging around 154 mg/dL, and by 9% the average reaches roughly 212 mg/dL. Each 1% increase in A1C corresponds to about a 29 mg/dL jump in average blood sugar.
These are averages with a range around them. Someone with a 7% A1C might have actual blood sugar swinging between 123 and 185 mg/dL throughout the day. The A1C smooths all of that into one number.
Target Levels for People With Diabetes
Diagnosis thresholds and management targets are two different things. Getting diagnosed at 6.5% doesn’t mean you need to get back below that number to be healthy. For most non-pregnant adults with diabetes, the general target is an A1C below 7.0%. That level is associated with significantly lower risks of the long-term complications diabetes can cause, like nerve damage and kidney problems.
Targets shift with age. For healthy adults over 65, the American Diabetes Association recommends a slightly relaxed goal of below 7.5%. For older adults with multiple health conditions, the target loosens further to below 8.0%, and for those with complex or poor overall health, below 8.5%. The reasoning is straightforward: pushing blood sugar too low in older adults increases the risk of dangerous drops (hypoglycemia), which can cause falls, confusion, and hospitalizations. A slightly higher A1C target reduces that risk without meaningfully increasing long-term complications in someone with a shorter treatment horizon.
The American College of Physicians takes a broader view, recommending a general target between 7.0% and 8.0% for most adults with type 2 diabetes.
How Often to Get Tested
If your blood sugar is well controlled and stable, testing every six months is sufficient. If you’re adjusting medications, changing your lifestyle approach, or your levels aren’t where they need to be, testing every three months makes more sense. Since A1C reflects a three-month window, testing more frequently than that doesn’t give the number enough time to shift meaningfully.
When A1C Results Can Be Misleading
A1C is reliable for most people, but certain conditions can skew the results. Iron deficiency anemia is the most well-documented culprit. When you’re low on iron, red blood cells live longer than usual, giving glucose more time to attach to hemoglobin. The result is a falsely elevated A1C that makes blood sugar control look worse than it actually is. This is particularly relevant for pregnant women, who are more prone to iron deficiency anemia and can be misdiagnosed with gestational diabetes based on an inflated A1C reading.
Vitamin B12 deficiency can cause similar distortions. Conditions that affect red blood cell turnover in the opposite direction, like significant blood loss or certain types of hemoglobin variants (common in people of African, Mediterranean, or Southeast Asian descent), can push A1C readings artificially low. If your A1C doesn’t seem to match your glucose meter readings, one of these factors could be the explanation.
Lowering Your A1C Through Lifestyle
For people in the prediabetes range or newly diagnosed with type 2 diabetes, lifestyle changes can produce dramatic results. Regular exercise and dietary shifts are the foundation. Walking about 4.5 kilometers (roughly 2.8 miles) in 45 minutes daily is the type of moderate activity that consistently lowers A1C in clinical practice.
Dietary changes that move the needle tend to share a few principles: prioritizing protein and fiber early in each meal (salads, beans, eggs), cutting added sugars, and reducing refined carbohydrates. These aren’t exotic interventions. They work by flattening the blood sugar spikes that drive glycation in the first place. Fiber slows digestion, protein promotes satiety, and eliminating added sugar removes the most direct source of glucose flooding.
The potential magnitude of change is striking. In documented cases of highly motivated individuals who combined consistent daily walking with structured dietary changes, A1C reductions of several percentage points within three months have been observed, sometimes enough to move from the diabetic range back to normal without medication. Those are exceptional cases, but even modest lifestyle changes typically lower A1C by 0.5 to 1.0 percentage points, which is clinically meaningful and enough to reduce complication risks.
Because A1C reflects a three-month average, you won’t see results overnight. But any sustained change in daily blood sugar will start bending the curve. If you check your A1C, make changes, and retest three months later, the new number will reflect nearly the full impact of what you’ve done differently.