ADA A1C Diagnostic Ranges Explained

July 14, 2026

The American Diabetes Association (ADA) sets three A1C ranges used to screen for and diagnose diabetes in adults. This doc explains what each range means, how a diagnosis is confirmed, and when an A1C result may not be trustworthy on its own.

The Three ADA Ranges

Category	A1C Range	Approximate eAG
Normal	Below 5.7%	Below 117 mg/dL
Prediabetes	5.7% – 6.4%	117–137 mg/dL
Diabetes	6.5% or higher	154+ mg/dL

These cutoffs come from the ADA’s annually updated Standards of Care in Diabetes and are echoed by the CDC and NIDDK. Run any of these percentages through the A1C calculator to see the exact eAG in both mg/dL and mmol/L, along with the IFCC mmol/mol equivalent.

Normal Range — Below 5.7%

An A1C under 5.7% shows no indication of diabetes or prediabetes based on this test alone. How often you should be re-screened in the future depends on individual risk factors such as age, weight, family history, and blood pressure — a healthcare provider sets that interval, not a fixed rule.

Prediabetes — 5.7% to 6.4%

Prediabetes means blood sugar is higher than normal but not yet at the diabetes threshold. It signals meaningfully elevated risk of progressing to type 2 diabetes. The ADA recommends lifestyle intervention (nutrition changes, physical activity, weight management where relevant) and re-testing at least once a year. Within this band, the ADA also notes that people at the higher end (A1C above 6.0%) are considered very high risk and often warrant more assertive follow-up.

Diabetes — 6.5% or Higher

An A1C of 6.5% or above meets the ADA’s diagnostic threshold for diabetes — but a single result is typically not enough on its own. Standard practice is to confirm with a repeat test on a separate day, unless the person already has classic diabetes symptoms (frequent urination, excessive thirst, unexplained weight loss) combined with a random plasma glucose of 200 mg/dL or higher, in which case a diagnosis can be made without a second confirmatory test.

Why Confirmation Matters

A1C can fluctuate slightly between lab draws due to normal biological variation and assay differences between labs. Confirming with a second test — ideally using the same testing method — protects against diagnosing someone based on a single borderline or erroneous result.

When A1C Alone Can Be Misleading

Because A1C is calculated from the lifespan and glucose exposure of red blood cells, anything that changes how long those cells circulate can distort the percentage independent of actual average glucose. According to the NIDDK, this includes:

Anemias, including iron-deficiency anemia
Hemoglobin variants such as sickle cell trait (HbS), HbC, or HbE
Recent significant blood loss or a blood transfusion
Chronic kidney disease or liver disease, which can alter red blood cell turnover
Pregnancy, which shortens red blood cell lifespan and can lower A1C even when glucose is elevated

In any of these situations, a provider may rely more heavily on direct glucose testing — fasting plasma glucose, an oral glucose tolerance test, or CGM data — rather than A1C alone. If you’re comparing your A1C to home meter readings and the numbers don’t seem to line up, one of these factors (or simple day-to-day glucose variability) may be why.

If you were recently given one of these results for the first time, the A1C calculator guide for newly diagnosed prediabetes and diabetes walks through what to do next. For a look at how people commonly misread these numbers, see common mistakes interpreting A1C and eAG results.

This page is educational and does not replace individualized medical advice — diagnostic decisions should always be made with a healthcare provider who has your full test history.