Prediabetes A1C Range (5.7–6.4%): What Your Number Means

The prediabetes A1C range is 5.7% to 6.4% (39–47 mmol/mol), according to the American Diabetes Association (ADA) and the CDC. An A1C below 5.7% is normal, and 6.5% or higher indicates diabetes, usually confirmed with a second test. Within the prediabetes range, the risk of type 2 diabetes rises disproportionately toward the top, but lifestyle changes can lower that risk and may bring your A1C back into the normal range.

This guide explains what the A1C test measures, what your specific number means, how it translates into average blood sugar, when the test can be misleading and what to do next.

A1C ranges at a glance

Category	A1C (%)	A1C (mmol/mol)	Estimated average glucose
Normal	below 5.7%	below 39	below about 117 mg/dL (6.5 mmol/L)
Prediabetes	5.7–6.4%	39–47	about 117–137 mg/dL (6.5–7.6 mmol/L)
Diabetes	6.5% or higher	48 or higher	about 140 mg/dL (7.8 mmol/L) or higher

These are the cut-offs used by the ADA, the CDC and the NIDDK (part of the NIH). Not every organization uses them:

International Expert Committee (2009) and the UK’s NICE: treat 6.0–6.4% (42–47 mmol/mol) as the high-risk range.
World Health Organization (WHO): uses 6.5% to diagnose diabetes but makes no formal recommendation for values below 6.5%.

So a 5.8% result counts as prediabetes in the US but would not be classed as high risk under NICE.

Estimated average glucose (eAG) comes from the A1C-Derived Average Glucose (ADAG) study: eAG (mg/dL) = 28.7 × A1C − 46.7. It is an estimate, not your personal average. In that study, an A1C of 6% matched an eAG of 126 mg/dL, but the study’s 95% interval ran from 100 to 152 mg/dL. To convert your own result, use our A1C calculator.

What the A1C test measures

A1C (also called HbA1c or glycated hemoglobin) measures the percentage of hemoglobin in your red blood cells that has glucose attached. Red blood cells regenerate roughly every three months, the CDC explains, so A1C reflects your average blood sugar over about the past three months. That makes it a useful big-picture number: a single meal doesn’t swing it the way it swings a finger-stick reading, and you don’t need to fast for it.

The ADA also accepts two glucose tests for prediabetes:

Fasting plasma glucose: 100–125 mg/dL (5.6–6.9 mmol/L)
2-hour oral glucose tolerance test (OGTT): 140–199 mg/dL (7.8–11.0 mmol/L)

Different tests can give different answers for the same person, which is one reason clinicians confirm abnormal results.

What your number means within the prediabetes A1C range

The NIDDK puts it simply: within the prediabetes A1C range, the higher the A1C, the greater the risk of diabetes. The ADA adds that risk is continuous and rises disproportionately at the higher end of the range.

A CDC systematic review put rough numbers on this. In studies that followed people across a broad range of A1C levels, estimated five-year diabetes incidence was:

A1C 5.5–6.0%: about 9–25%
A1C 6.0–6.5%: about 25–50%

These bands don’t line up exactly with 5.7% and 6.4%. Your own risk also depends on other risk factors the CDC lists, such as overweight, being 45 or older, a parent or sibling with type 2 diabetes and physical inactivity.

In practical terms:

5.7–5.9%: Your risk is raised, though lower than at the top of the range. This is a good time to act.
6.0–6.4%: The ADA considers an A1C above 6.0% very high risk and advises more intensive prevention and closer follow-up. It also says metformin should be considered for some high-risk adults, especially those aged 25–59 with a BMI of 35 or higher, higher fasting glucose and an A1C of 6.0% or more, and for people who had gestational diabetes. Whether medication is right for you is a decision to make with your clinician.

When A1C can be misleading

A1C depends on normal red blood cells and hemoglobin, so some conditions distort it. According to the NIDDK, CDC and ADA:

Anemia: iron-deficiency anemia can make A1C falsely high.
Kidney or liver disease, blood loss and some treatments: kidney failure, liver disease, recent blood loss or transfusion, hemodialysis and erythropoietin treatment can all change A1C.
Pregnancy and some medicines: the CDC lists early or late pregnancy, opioids and some HIV medications.
Inherited blood conditions: if you’re of African, Mediterranean or Southeast Asian descent, or have family members with sickle cell disease or thalassemia, the NIDDK says an A1C test can be unreliable. The ADA adds that a genetic variant affecting the enzyme G6PD, carried by about 11% of Black Americans, is linked to lower A1C results.

In situations like these, the ADA says plasma glucose tests should be used for diagnosis instead. If your A1C doesn’t match your other test results, ask your clinician why. The ADA says a consistent, substantial mismatch should be followed up.

Should you repeat an abnormal A1C?

Usually, yes. The NIDDK advises that if you have no symptoms but an A1C shows diabetes or prediabetes, you should have a repeat test on a different day, using A1C or another diabetes test, to confirm the diagnosis. The ADA also accepts abnormal results on two different tests done at the same time.

After a prediabetes result:

The ADA recommends testing for diabetes at least once a year, adjusted to your individual risk.
The CDC says your doctor will likely recommend repeating A1C every 1 to 2 years.
Because A1C reflects about three months, a retest much sooner than that won’t fully show the effect of new habits.

Who should be tested in the first place? The US Preventive Services Task Force recommends screening adults aged 35 to 70 with overweight or obesity. The CDC recommends an A1C test if you’re over 45, or younger with overweight and any other risk factor. Not sure where you stand? Try our prediabetes risk test.

What to do after a prediabetes A1C result

Confirm it. Ask whether a repeat A1C or a glucose-based test is needed, especially if you have a condition that can distort A1C.
Check your heart risk factors too. The ADA notes that prediabetes is linked to higher cardiovascular risk and suggests screening for and treating risk factors such as high blood pressure and cholesterol.
Ask about a structured program. Ask whether a CDC-recognized National Diabetes Prevention Program lifestyle change program is available near you or online.
Pick two habits to start this week, such as a walk after dinner and swapping sugary drinks for water, rather than overhauling everything at once.
Agree on a retest date with your clinician.

How to lower your A1C out of the prediabetes range

The strongest evidence comes from structured lifestyle programs:

In the Diabetes Prevention Program trial of 3,234 adults at high risk, a lifestyle program with goals of at least 7% weight loss and 150 minutes of activity a week reduced new cases of type 2 diabetes by 58% over about three years, compared with 31% for metformin (both versus placebo). The CDC’s National Diabetes Prevention Program cites the same 58% figure, and 71% for people over 60.
The ADA’s 2026 Standards of Care recommend that adults with overweight or obesity at high risk join a prevention program aiming for a weight loss of at least 5–7% and at least 150 minutes a week of moderate activity. For people with prediabetes, the ADA recommends an evidence-based eating pattern, such as Mediterranean or low-carbohydrate; DASH and plant-based patterns are also listed as appropriate.
The CDC says prediabetes can be reversed with changes such as losing a small amount of weight, making healthy eating choices and getting more physically active.

Practical starting points include a short walk after meals, filling half your plate with non-starchy vegetables (the CDC’s plate method) and muscle-strengthening activity at least two days a week, as the CDC recommends for all adults. Our guides on how to reverse prediabetes, how to stabilize blood sugar and how to lower blood sugar without a CGM go deeper.

Between lab tests, it can help to see how your daily habits line up with your results. Helsa, free to download on iOS and Android, offers blood marker analysis, photo and voice meal logging and daily reports, and works with wearables like Apple Health, with no CGM needed.

Frequently asked questions

Is an A1C of 5.7% bad?

It is the lowest number in the ADA’s prediabetes range. Your risk of type 2 diabetes is higher than normal, though lower than at the top of the range. It is not a diabetes diagnosis, and it is a good time to act, since lifestyle changes can lower your risk.

Is an A1C of 6.4% almost diabetes?

Yes. It is the top of the prediabetes range, just below the 6.5% diabetes threshold, and the ADA considers A1C levels above 6.0% very high risk. Talk with your clinician about confirming the result, a prevention plan and whether medication makes sense for you.

Can A1C go from prediabetes back to normal?

It can. The CDC says prediabetes can be reversed with lifestyle changes such as modest weight loss, healthier eating and more activity. It doesn’t happen for everyone, so keep testing as your clinician advises.

What is the difference between A1C and fasting glucose?

Fasting glucose is a snapshot of your blood sugar after an overnight fast. A1C reflects your average over about three months. Both are used to diagnose prediabetes, and they do not always agree.

Does the prediabetes A1C range change with age?

Under ADA and CDC criteria, the same cut-offs apply to all adults. A1C is not used the same way in pregnancy, and some countries, such as the UK, use a different range.

How quickly can I lower my A1C?

A1C reflects roughly the past three months, so it takes about that long for new habits to show fully in your result. How much it changes varies from person to person, so ask your clinician when to retest.

This article is for general education and is not medical advice. Talk with your healthcare provider about your results.

Sources

CDC. A1C Test for Diabetes and Prediabetes
NIDDK. The A1C Test & Diabetes
American Diabetes Association. Diagnosis
ADA Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care, 2026.
ADA Professional Practice Committee. 3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes—2026. Diabetes Care, 2026.
Nathan DM, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care, 2008.
Zhang X, et al. A1C level and future risk of diabetes: a systematic review. Diabetes Care, 2010.
Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med, 2002.
US Preventive Services Task Force. Screening for prediabetes and type 2 diabetes: recommendation statement. JAMA, 2021.
CDC. Prediabetes – Your Chance to Prevent Type 2 Diabetes
CDC. Preventing Type 2 Diabetes
CDC. Diabetes Meal Planning
CDC. Adult Activity: An Overview
NICE. Type 2 diabetes: prevention in people at high risk (PH38). 2012, updated 2017.
WHO. Use of glycated haemoglobin (HbA1c) in diagnosis of diabetes mellitus: abbreviated report of a WHO consultation. 2011.