A good A1C level is below 5.7%, which falls in the normal range and translates to an estimated average blood sugar of about 117 mg/dL or less. If you already have diabetes, the target shifts: most people with type 2 diabetes aim for 7% to 8%, though your ideal number depends on your age, overall health, and how long you’ve had the condition.
What the A1C Ranges Mean
The A1C test measures the percentage of your red blood cells that have sugar attached to them. Because red blood cells live about three months, the result reflects your average blood sugar over that window, not just a single moment. The CDC uses three ranges for diagnosis:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A result in the prediabetes range means your blood sugar is higher than it should be but hasn’t crossed the diabetes threshold. It’s a meaningful warning sign. Roughly 80% of people with prediabetes don’t know they have it, and without changes, many will progress to type 2 diabetes within several years.
A1C Targets If You Have Diabetes
Once you have a diabetes diagnosis, “good” no longer means below 5.7%. Pushing your A1C too low with medication can cause dangerous drops in blood sugar, so treatment targets are deliberately higher than the normal range. Updated guidance from the American College of Physicians recommends 7% to 8% for most adults with type 2 diabetes, because going below 7% with medication hasn’t been shown to reduce the risk of heart attacks or death.
If your A1C drops below 6.5% on medication, your doctor may actually reduce your treatment. Evidence shows that driving the number that low with drugs causes more harm than benefit for most people. The exception is if you’re managing your blood sugar through diet and exercise alone, in which case a lower A1C simply reflects good metabolic health without the added risks of medication side effects.
Younger adults who are otherwise healthy and expected to live at least 15 more years may benefit from a slightly stricter target, closer to 7%. For adults over 80, or anyone with serious chronic conditions or a shorter life expectancy, the focus shifts away from hitting a specific number. The priority becomes avoiding symptoms of high blood sugar, like excessive thirst, frequent urination, and fatigue, rather than chasing a target on paper.
Why Each Percentage Point Matters
Small changes in A1C have outsized effects on your long-term health. The landmark United Kingdom Prospective Diabetes Study followed over 4,500 people with diabetes for 15 years and found that every 1% reduction in A1C was linked to roughly a 25% reduction in complications affecting the eyes, kidneys, and nerves. The strongest finding was a 33% drop in a marker of kidney damage.
The relationship with heart disease was less clear. That study didn’t definitively show that lowering A1C reduced the risk of heart attacks. This is part of why guidelines don’t push for the lowest possible number: the proven benefits are primarily in protecting smaller blood vessels, and those benefits need to be weighed against the risks of aggressive treatment.
How A1C Translates to Daily Blood Sugar
If you check your blood sugar at home, it helps to know what your A1C means in everyday numbers. The American Diabetes Association uses a formula to convert A1C into estimated average glucose (eAG), measured in mg/dL:
- 6% A1C: ~126 mg/dL average
- 6.5%: ~140 mg/dL
- 7%: ~154 mg/dL
- 7.5%: ~169 mg/dL
- 8%: ~183 mg/dL
- 9%: ~212 mg/dL
- 10%: ~240 mg/dL
Keep in mind this is an average. Your blood sugar naturally swings throughout the day, peaking after meals and dropping overnight. Two people with the same A1C could have very different daily patterns. One might run consistently at 154 mg/dL, while another swings between 80 and 230 mg/dL. Continuous glucose monitors capture those swings in a way that A1C alone cannot.
When A1C Results Can Be Misleading
The A1C test is reliable for most people, but certain conditions can skew the results in either direction. Anything that changes how long your red blood cells survive will affect the reading, since the test depends on sugar accumulating on those cells over their lifespan.
Conditions that shorten red blood cell life, like hemolytic anemia or recovery from significant blood loss, will make your A1C appear falsely low. Your blood sugar might actually be higher than the test suggests. On the other end, iron deficiency anemia tends to push A1C readings falsely high, which means you could look like you have worse blood sugar control than you actually do. This is especially relevant during late pregnancy, when iron deficiency is common and can inflate A1C even in women without diabetes.
Sickle cell trait and other hemoglobin variants also interfere with many A1C testing methods. If you carry one of these traits, your results may not accurately reflect your blood sugar, and your doctor might use an alternative test like fructosamine or glycated albumin instead. Chronic kidney disease, particularly in people on dialysis, creates another complication: A1C tends to underestimate actual blood sugar levels in these patients.
If you have any of these conditions and your A1C result doesn’t match how you feel or what your home glucose readings show, it’s worth asking whether the test is giving you an accurate picture.
How to Improve Your A1C
Because A1C reflects a three-month average, changes take time to show up. Most doctors recheck the test every three to six months after a treatment change. The strategies that lower A1C are the same ones that improve blood sugar day to day: reducing refined carbohydrates, increasing physical activity, losing even a modest amount of weight (5% to 7% of body weight makes a measurable difference in prediabetes), and taking prescribed medications consistently.
Exercise has a direct effect because working muscles pull sugar out of your blood without needing as much insulin. Both aerobic activity and resistance training help, and the combination tends to be more effective than either one alone. Even regular walking after meals can blunt the post-meal blood sugar spikes that contribute most to a high A1C.
If your A1C is in the prediabetes range, lifestyle changes alone can often bring it back below 5.7% and significantly reduce your risk of progressing to diabetes. If you’re already managing diabetes, the goal is steady, sustainable improvement rather than dramatic drops, which can sometimes signal too-aggressive medication use and increase your risk of low blood sugar episodes.