A good hemoglobin A1c level is below 5.7%, which is considered normal. This number represents your average blood sugar over the past two to three months, expressed as a percentage. Unlike a finger-stick glucose reading that captures a single moment, A1c gives a broader picture of how your body has been managing blood sugar over time.
The Three A1c Ranges
The CDC uses three clear cutoffs to categorize A1c results:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
If your result falls in the prediabetes range, it means your blood sugar is higher than it should be but hasn’t crossed into diabetes territory. About one in three American adults have prediabetes, and many don’t know it. The good news is that prediabetes is reversible with lifestyle changes, while a result at or above 6.5% typically leads to a diabetes diagnosis (usually confirmed with a second test).
What Your A1c Means in Everyday Blood Sugar
A1c percentages can feel abstract. It helps to translate them into the average blood sugar your body has been running. Here’s how some common A1c values map to estimated average glucose:
- 5.4%: about 108 mg/dL
- 5.7%: about 117 mg/dL
- 6.0%: about 125 mg/dL
- 6.5%: about 140 mg/dL
- 7.0%: about 154 mg/dL
- 8.0%: about 183 mg/dL
- 9.0%: about 212 mg/dL
- 10.0%: about 240 mg/dL
Each full percentage point on the A1c scale corresponds to roughly a 29 mg/dL increase in average blood sugar. So the difference between a 6.0% and a 7.0% is the difference between an average glucose of 125 and 154 mg/dL.
Target A1c if You Have Diabetes
If you’re already living with diabetes, “good” shifts from “normal” to “well-managed.” For most adults with type 1 or type 2 diabetes, the general target is below 7.0%. That corresponds to an average blood sugar of about 154 mg/dL and is associated with significantly lower risk of complications affecting the eyes, kidneys, and nerves.
But that 7.0% target isn’t universal. Your ideal number depends on your age, overall health, how long you’ve had diabetes, and how prone you are to low blood sugar episodes. Some people safely aim lower, while others benefit from a higher ceiling.
Older Adults
For healthy older adults with a life expectancy beyond 10 years, a target below 7.5% is generally appropriate. For those managing multiple chronic conditions, below 8.0% is often more realistic and safer, because aggressively lowering blood sugar in this group increases the risk of dangerous lows. Older adults in poor health or with significant cognitive decline may have individualized targets as high as 8.5%, which translates to an average glucose around 200 mg/dL. At that point, the priority shifts to avoiding severe highs and lows rather than chasing a specific number.
Children and Teens
For children and adolescents with type 1 diabetes, the International Society for Pediatric and Adolescent Diabetes recommends a target of 6.5% or below when the child has access to continuous glucose monitors and automated insulin delivery systems. Without those technologies, the recommended target is 7.0% or below. These targets apply only when they can be reached safely, without frequent low blood sugar episodes or a heavy burden on quality of life.
During Pregnancy
Blood sugar control matters more during pregnancy than at almost any other time. For women with diabetes who are planning a pregnancy, the goal is an A1c below 7% and as close to 6% as possible, without causing dangerous lows. Once pregnant, the target tightens further to below 6% if it can be achieved safely. These stricter targets reflect the fact that even moderately elevated blood sugar during pregnancy increases risks for both mother and baby.
How Lifestyle Changes Affect A1c
If your A1c is in the prediabetes range, diet and exercise changes can bring it down, though the effect is modest in absolute terms. The Diabetes Prevention Program trial found that intensive lifestyle intervention (focused on weight loss through diet and increased physical activity) lowered A1c by about 0.10 percentage points over six months. A later study confirmed similar results: high-dose behavioral weight loss treatment produced an average A1c reduction of 0.11 percentage points, with about 37% of participants achieving a clinically meaningful drop of 0.3% or more.
Those numbers sound small, but they matter. When your A1c is 5.9%, a 0.2-point drop puts you back in the normal range. For people with diabetes, lifestyle changes work alongside medication and can sometimes make the difference between needing an additional drug or not. The most effective interventions combine regular physical activity, dietary changes, and meaningful weight loss, typically 5% to 7% of body weight.
When Your A1c May Not Be Accurate
The A1c test measures how much sugar has attached to hemoglobin, the protein in red blood cells that carries oxygen. Anything that changes your red blood cells or hemoglobin can throw off the result.
Iron deficiency anemia is one of the most common culprits. It causes A1c to read falsely high, which means you could get a prediabetes result when your actual blood sugar is normal. This is especially relevant during late pregnancy, when iron deficiency is common. Treating the iron deficiency brings the A1c back in line with reality.
Conditions that shorten the lifespan of red blood cells, like hemolytic anemia or recovery from significant blood loss, push A1c in the opposite direction, making it falsely low. Your red blood cells haven’t been around long enough to accumulate sugar, so the test underestimates your true average glucose.
Sickle cell trait and other hemoglobin variants can also interfere with results, depending on the lab method used. People with kidney failure face a particularly complicated picture: kidney-related anemia, changes to hemoglobin structure, and the effects of dialysis or transfusions can all distort the reading. In these situations, alternative measures like glycated albumin or direct glucose monitoring give a more reliable picture of blood sugar control.
If you have any of these conditions and your A1c result doesn’t match what your day-to-day glucose readings suggest, the discrepancy is worth raising with your doctor. The A1c is a useful tool, but it’s not perfect for everyone.