A normal A1C level is below 5.7%. This number represents your average blood sugar over the past two to three months, making it one of the most reliable snapshots of how your body handles glucose day to day. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes.
What the A1C Test Actually Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more glucose circulating in your blood over time, the more hemoglobin gets coated. Since red blood cells live about three months before your body replaces them, measuring the percentage of hemoglobin with glucose attached gives a reliable average of your blood sugar levels over that entire lifespan.
This is what makes A1C different from a finger stick or fasting glucose test, which only captures a single moment. You could have a perfect fasting glucose reading the morning of your test but still have an elevated A1C if your blood sugar has been running high after meals for weeks. The A1C catches patterns that a one-time reading misses.
The Three A1C Ranges
The diagnostic cutoffs used by most clinicians break down like this:
- Below 5.7%: Normal. Your body is managing blood sugar effectively.
- 5.7% to 6.4%: Prediabetes. Blood sugar is higher than it should be but hasn’t crossed the diabetes threshold. This is the window where lifestyle changes, like adjusting your diet and increasing physical activity, can make the biggest difference.
- 6.5% or higher: Diabetes. This result, confirmed by a second test, is typically enough for a diagnosis.
To put these percentages in more concrete terms, an A1C of 5.7% corresponds to an estimated average glucose of roughly 117 mg/dL. An A1C of 7%, a common management target for people already diagnosed with diabetes, translates to an average glucose of about 154 mg/dL.
Targets for People With Diabetes
If you’ve already been diagnosed, “normal” shifts from a diagnostic label to a management goal, and that goal isn’t the same for everyone. For most nonpregnant adults with diabetes, the American Diabetes Association suggests aiming for an A1C of 7% or below. But this target gets adjusted based on age, overall health, and the risk of blood sugar dropping too low.
For healthy older adults, a goal below 7.5% is often more appropriate. Older adults with significant health conditions may aim for 8% or lower, and those with severe comorbidities or cognitive decline may have an even more relaxed target, around 8.5%, to avoid the dangers of hypoglycemia. Pushing A1C too low with medication can cause blood sugar crashes that are especially risky for older people, so the tradeoff between tight control and safety matters more with age.
A1C Targets During Pregnancy
Pregnancy changes how the test works. Red blood cell turnover speeds up, which naturally lowers A1C readings in all pregnant people, whether or not they have diabetes. For those managing diabetes during pregnancy, the ideal goal is an A1C below 6% if it can be reached without frequent low blood sugar episodes. If that’s not safely achievable, the target may be relaxed to below 7%.
Before conception, an A1C below 6.5% is recommended to reduce the risk of complications like birth defects, preeclampsia, and preterm delivery. During pregnancy itself, though, A1C is considered a secondary tool. It doesn’t capture post-meal blood sugar spikes very well, and those spikes are what most directly affect fetal growth. Daily glucose monitoring gives a more complete picture.
When A1C Results Can Be Misleading
The test relies on hemoglobin behaving in a predictable way, and several conditions can throw it off. Anything that changes how long your red blood cells survive or how hemoglobin interacts with glucose can push your result artificially higher or lower.
Known factors that can produce inaccurate A1C readings include:
- Severe anemia: Altered red blood cell counts skew the measurement.
- Kidney failure or liver disease: Both can change red blood cell lifespan.
- Blood disorders like sickle cell anemia or thalassemia: These involve different forms of hemoglobin that some A1C tests can’t measure accurately.
- Recent blood loss or transfusions: Introducing new red blood cells dilutes the glucose-coated ones.
- Certain medications: Opioids and some HIV medications can interfere with results.
- Pregnancy: Particularly early or late pregnancy, due to changes in blood volume and red blood cell turnover.
If any of these apply to you, your provider may rely on alternative tests like fructosamine, which measures blood sugar averages over a shorter two- to three-week window, or use direct glucose monitoring instead.
Hemoglobin Variants and Ancestry
The most common form of hemoglobin is called hemoglobin A, and it’s what standard A1C tests are designed to measure. But less common hemoglobin variants exist, and they’re more prevalent in people whose ancestors came from Africa, South and Southeast Asia, or the Mediterranean. These variants don’t increase your risk of diabetes, but they can cause certain A1C tests to read falsely high or falsely low.
If your results seem inconsistent with your daily glucose readings, or if you know you carry a hemoglobin variant, your provider can use a testing method that isn’t affected by it. The important thing is that a discrepancy between how you feel, what your home glucose readings show, and what your A1C says is worth investigating rather than ignoring.
How Often to Get Tested
If your A1C is normal and you have no risk factors for diabetes, periodic screening as part of routine bloodwork is generally sufficient. Adults 45 and older, or younger adults with risk factors like obesity, a family history of diabetes, or a history of gestational diabetes, benefit from more regular testing.
For people with prediabetes, retesting every one to two years helps track whether blood sugar levels are holding steady or trending upward. If you’re managing diabetes, most guidelines recommend A1C testing two to four times per year, depending on how stable your blood sugar control is and whether your treatment plan has recently changed. The three-month average the test captures means testing more frequently than every three months won’t give you meaningfully new information.