A good A1c for most adults is below 5.7%, which is considered normal. This number represents your average blood sugar over the past three months, expressed as a percentage. If you already have diabetes, the target shifts higher, and the “good” number depends on your age, health, and life circumstances.
The Standard A1c Ranges
The CDC uses three straightforward categories:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
If you don’t have diabetes and your result comes back under 5.7%, your blood sugar management is in a healthy range. A result between 5.7% and 6.4% means your blood sugar has been running higher than normal, but not high enough for a diabetes diagnosis. This prediabetes range is a signal that changes now can prevent progression.
What A1c Means in Everyday Blood Sugar
A1c measures how much sugar has attached to your red blood cells over their roughly three-month lifespan. The higher your blood sugar runs day to day, the more sugar sticks to those cells, and the higher your percentage climbs. The American Diabetes Association provides a formula to translate A1c into an estimated average glucose (eAG) in mg/dL: multiply your A1c by 28.7, then subtract 46.7.
Here’s what that looks like in practice:
- A1c of 5.7%: average blood sugar around 117 mg/dL
- A1c of 6%: average blood sugar around 126 mg/dL
- A1c of 6.5%: average blood sugar around 140 mg/dL
- A1c of 7%: average blood sugar around 154 mg/dL
- A1c of 8%: average blood sugar around 183 mg/dL
- A1c of 9%: average blood sugar around 212 mg/dL
These conversions help you connect a single lab number to what’s actually happening in your bloodstream every day. An A1c of 7% doesn’t mean your blood sugar sits at 154 all the time. It could swing between 80 and 250, but the weighted average lands near 154.
Targets If You Have Diabetes
For most adults with type 1 or type 2 diabetes, the widely recommended goal is an A1c below 7%. That level is associated with significantly lower risk of complications affecting the eyes, kidneys, and nerves. Some people aim for even tighter control, closer to 6.5%, especially if they can reach it without frequent episodes of low blood sugar.
But “good” is not one-size-fits-all. Several factors shift the target:
- Older adults with other health conditions: A target of 8% or lower is often more appropriate for people who are frail, have multiple chronic illnesses, or have a life expectancy under 10 years. For those with severe health challenges or cognitive decline, the target may be relaxed further to below 8.5%, which corresponds to an average blood sugar around 200 mg/dL. The priority here is avoiding dangerous blood sugar swings rather than hitting a tight number.
- Children with type 1 diabetes: Most guidelines recommend below 7.5%. Kids with type 2 diabetes generally aim for below 7%.
- Pregnancy: Targets tighten considerably. Before conception, the goal is typically 6.5% or lower. During pregnancy, most guidelines recommend keeping A1c below 6% to reduce the risk of complications for both mother and baby.
The reason targets vary so much comes down to a tradeoff. Pushing A1c lower requires more aggressive blood sugar management, which increases the risk of hypoglycemia (blood sugar dropping dangerously low). For a healthy 35-year-old with decades of life ahead, the long-term benefit of tight control outweighs that risk. For an 80-year-old on multiple medications, a severe low blood sugar episode can cause falls, confusion, or hospitalization, making a slightly higher A1c the safer choice.
How Quickly A1c Can Change
Because the test reflects a three-month average, it takes roughly that long to see the full impact of any change you make. Your most recent weeks weigh more heavily than the first weeks of that window, so meaningful shifts can start showing up within six to eight weeks.
A Johns Hopkins study of 251 people with diabetes found that combining aerobic exercise with strength training for about six months lowered A1c by nearly 1 percentage point. That may sound modest, but a 1-point drop is enough to reduce the risk of diabetes-related complications to small blood vessels by about 35%. Dietary changes, weight loss, and medication adjustments can produce similar or larger shifts over the same timeframe.
If your A1c is in the prediabetes range, even a small improvement matters. Dropping from 6.3% to 5.6% moves you from prediabetes back into the normal category, and the lifestyle changes that get you there (regular physical activity, reducing refined carbohydrates, modest weight loss) also lower your risk of heart disease independently of the number.
When Your A1c May Not Be Accurate
The test works by measuring sugar attached to hemoglobin inside red blood cells. Anything that changes how long your red blood cells survive or alters the structure of your hemoglobin can throw off the result.
Iron deficiency anemia can push A1c readings falsely high, which is especially relevant during late pregnancy when iron stores tend to drop. Conditions that destroy red blood cells faster than normal, like hemolytic anemia or significant blood loss, have the opposite effect, making A1c appear falsely low because the cells haven’t been around long enough to accumulate sugar.
People with sickle cell trait or disease, as well as other hemoglobin variants, may get unreliable results regardless of the testing method. Kidney failure can also distort A1c. In patients on dialysis, the test tends to underestimate actual blood sugar levels. For these situations, alternative markers like fructosamine or glycated albumin give a more reliable picture.
If you have any of these conditions and your A1c result doesn’t match what your daily blood sugar readings suggest, it’s worth discussing alternative testing with your provider. The number is only useful if it accurately reflects what’s happening in your body.