A healthy A1C level is below 5.7%, according to the American Diabetes Association. This number represents your average blood sugar over the past two to three months, making it one of the most useful snapshots of how your body handles glucose over time. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes.
How the A1C Test Works
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more glucose circulating in your blood, the more hemoglobin gets coated. Since red blood cells live about three months, measuring the percentage of hemoglobin with glucose attached gives a reliable picture of your blood sugar over that entire window, not just a single moment in time.
This is what makes A1C different from a finger-stick glucose reading or a fasting blood sugar test. Those measure what’s happening right now. A1C captures the bigger trend, which is why it’s used for both diagnosing diabetes and monitoring how well blood sugar is being managed over time.
What the Numbers Mean
The three categories are straightforward:
- Below 5.7%: Normal. Your body is processing glucose well.
- 5.7% to 6.4%: Prediabetes. Blood sugar is higher than ideal and trending in the wrong direction.
- 6.5% or higher: Diabetes. Typically confirmed with a second test.
To put these percentages in more concrete terms, you can convert A1C to an estimated average glucose. An A1C of 6.0% corresponds to an average blood sugar of about 126 mg/dL. At 6.5%, the diabetes threshold, average blood sugar sits around 140 mg/dL. At 7.0%, it’s roughly 154 mg/dL. The formula behind this conversion is simple: multiply your A1C by 28.7, then subtract 46.7 to get your estimated average glucose in mg/dL.
These numbers help bridge the gap between a percentage that can feel abstract and the blood sugar readings you might already be familiar with from a glucose meter.
What Prediabetes Actually Means
Landing in the 5.7% to 6.4% range doesn’t mean you have diabetes, but it does mean your body is struggling to keep blood sugar in check. Insulin resistance is typically building, and without changes, the trajectory points toward type 2 diabetes.
The good news is that prediabetes is genuinely reversible. Weight loss of even 5% to 7% of body weight, combined with regular physical activity, has been shown to significantly reduce the risk of progressing to diabetes. If your A1C comes back in this range, it’s an early warning with a wide window for course correction, not a diagnosis you’re stuck with.
Different Targets for Different People
The under-5.7% target applies to people without diabetes. For those already managing type 2 diabetes, the goal shifts. Most guidelines recommend keeping A1C below 7.0%, but this isn’t universal, and pushing too low can actually cause harm in certain groups.
For adults over 65, tighter control often does more damage than good. Aggressively lowering A1C below 7.0% in older adults increases the risk of dangerously low blood sugar episodes, which can lead to falls, confusion, and hospitalization. Choosing Wisely Canada outlines a practical framework: healthy older adults with a long life expectancy can aim for 7.0% to 7.5%, those with moderate health conditions and a life expectancy under 10 years can target 7.5% to 8.0%, and people with multiple serious conditions may be best served by a target of 8.0% to 8.5%.
The takeaway is that “healthy” A1C depends on context. For a 35-year-old without diabetes, 5.4% is excellent. For a 78-year-old on insulin, 7.5% might be the safest and most appropriate goal.
When and How Often to Get Tested
The U.S. Preventive Services Task Force recommends A1C screening for adults over 45. If you’re younger than 45 but carry extra weight and have other risk factors (family history, sedentary lifestyle, history of gestational diabetes), testing is also recommended.
If your result comes back normal, retesting every three years is a reasonable schedule for most people. Those with prediabetes will typically be tested more frequently, often annually, to track whether lifestyle changes are working. People with diabetes usually get tested two to four times per year depending on how stable their blood sugar management is.
Conditions That Can Skew Your Results
A1C is reliable for most people, but certain medical conditions can push results higher or lower than your actual blood sugar warrants. Because the test depends on hemoglobin and red blood cells, anything that changes how those function can interfere.
Iron-deficiency anemia, chronic kidney disease, and conditions that shorten the lifespan of red blood cells (like heavy bleeding) can all produce inaccurate results. In some cases, A1C reads falsely high, which could lead to unnecessary treatment. In others, it reads falsely low, which could mask a real problem.
Hemoglobin variants, which are inherited differences in the structure of hemoglobin itself, can also affect accuracy. These variants are more common among people with ancestry from Africa, South and Southeast Asia, and the Mediterranean. Having a hemoglobin variant doesn’t change your diabetes risk, but it can change what your A1C test shows. Some lab methods produce falsely high results with certain variants, while others produce falsely low results. For people with specific hemoglobin conditions like sickle cell disease (HbSS, HbCC, or HbSC), the A1C test is unreliable enough that alternative blood sugar monitoring methods should be used instead.
If you have anemia, kidney disease, or know you carry a hemoglobin variant, it’s worth flagging this when your A1C results come in. Your doctor may confirm results with a fructosamine test or continuous glucose monitoring to get a more accurate picture.
How to Lower Your A1C
Because A1C reflects a three-month average, changes don’t show up overnight. Most people see meaningful shifts within two to three months of sustained effort. The primary levers are the same ones that improve metabolic health broadly.
Regular physical activity improves how your cells respond to insulin, which directly lowers blood sugar. Both aerobic exercise (walking, cycling, swimming) and resistance training help, and combining the two is more effective than either alone. Even 150 minutes per week of moderate activity, roughly 30 minutes five days a week, makes a measurable difference.
Dietary changes that reduce refined carbohydrates and added sugars tend to lower A1C most noticeably, since these foods spike blood sugar the fastest. Replacing them with fiber-rich vegetables, whole grains, lean proteins, and healthy fats creates a more gradual rise and fall in blood sugar throughout the day. Weight loss, even modest amounts, improves insulin sensitivity and can shift A1C downward by several tenths of a percentage point.
Sleep and stress also play underappreciated roles. Poor sleep and chronic stress both raise cortisol, which in turn raises blood sugar. Addressing these won’t single-handedly fix an elevated A1C, but they remove obstacles that make the other changes less effective.