Prediabetic Range for A1c

The prediabetic range for Hemoglobin A1c (HbA1c) is 5.7% to 6.4% (39-47 mmol/mol), as defined by the American Diabetes Association. 1, 2

Diagnostic Criteria for Prediabetes

Prediabetes can be diagnosed using any of the following criteria:

HbA1c: 5.7-6.4% (39-47 mmol/mol) 1
Fasting Plasma Glucose (FPG): 100-125 mg/dL (5.6-6.9 mmol/L), known as Impaired Fasting Glucose (IFG) 1
2-hour Plasma Glucose during 75g Oral Glucose Tolerance Test (OGTT): 140-199 mg/dL (7.8-11.0 mmol/L), known as Impaired Glucose Tolerance (IGT) 1

The risk of developing diabetes is not uniform across the prediabetic A1c range:

A1c 5.7-6.0%: 5-year diabetes incidence of 9-25% 1
A1c 6.0-6.4%: 5-year diabetes incidence of 25-50%, with relative risk approximately 20 times higher compared to those with A1c of 5.0% 1, 2

This risk gradient suggests the need for more intensive intervention and monitoring for those with A1c levels above 6.0% 2

All individuals with A1c in the prediabetic range should be informed about their increased risk for both diabetes and cardiovascular disease 1, 2
Preventive strategies focusing on weight loss and increased physical activity are recommended for all individuals with prediabetes 2
More vigilant follow-up is particularly important for those with A1c levels above 6.0% due to their substantially higher risk 1, 2
Evidence from the Diabetes Prevention Program shows that lifestyle interventions are effective for people across the prediabetic A1c spectrum 1, 2

The risk of developing diabetes is continuous, extending below the lower limit of the prediabetic range and becoming disproportionately greater at higher A1c levels 1
The World Health Organization and some other diabetes organizations define the lower limit of Impaired Fasting Glucose at 110 mg/dL (6.1 mmol/L), which differs from the ADA's 100 mg/dL (5.6 mmol/L) cutoff 1
Baseline A1c has been shown to be a stronger predictor of subsequent diabetes and cardiovascular events than fasting glucose in many populations 1
Recent research suggests that the positive predictive value of A1c for diagnosing prediabetes may be lower than previously thought, with one study showing only 39.4% of patients with A1c-based prediabetes actually having glucose-defined prediabetes on OGTT 3
Body mass index (BMI) and A1c are independently associated with progression to diabetes, suggesting that weight management should be prioritized in prediabetic patients 4, 5

Testing for prediabetes should be considered in adults who are overweight or obese (BMI ≥25 kg/m² or ≥23 kg/m² in Asian Americans) and have additional risk factors 1
For all people without risk factors, testing should begin at age 45 years 1
If tests are normal, repeat testing at a minimum of 3-year intervals is recommended 1