HbA1c Range for Prediabetes

The HbA1c range for prediabetes is 5.7% to 6.4% (39 to 46 mmol/mol) according to the American Diabetes Association guidelines. 1

Definition and Diagnostic Criteria

Prediabetes represents an intermediate stage between normal glucose regulation and diabetes, characterized by:

HbA1c levels of 5.7% to 6.4% (39 to 46 mmol/mol) 1
Fasting plasma glucose (FPG) of 100 mg/dL to 125 mg/dL (5.6 to 6.9 mmol/L), also known as impaired fasting glucose (IFG) 1
2-hour plasma glucose during 75-g oral glucose tolerance test (OGTT) of 140 mg/dL to 199 mg/dL (7.8 to 11.0 mmol/L), also known as impaired glucose tolerance (IGT) 1

The risk of progression to diabetes is not uniform across the prediabetes HbA1c range:

HbA1c 5.7% to 6.0% (39 to 42 mmol/mol): 5-year risk of developing diabetes ranges from 9% to 25% 1
HbA1c 6.0% to 6.4% (42 to 46 mmol/mol): 5-year risk increases to 25% to 50%, with a relative risk approximately 20 times higher compared to those with HbA1c of 5.0% 1

Baseline HbA1c is a stronger predictor of subsequent diabetes and cardiovascular events than fasting glucose in community-based studies 1
Risk of progression to diabetes follows HbA1c levels as a continuum, with higher values associated with disproportionately greater risk 1
Approximately 10% of people with prediabetes progress to diabetes each year in the US 2
Individuals with both elevated HbA1c (5.7-6.4%) and impaired fasting glucose have substantially higher risk of progression to diabetes than those with either criterion alone 3

The risk for developing diabetes follows HbA1c as a continuum, becoming disproportionately greater at the higher end of the prediabetes range 1
More intensive follow-up and interventions should be considered for those with HbA1c levels above 6.0%, who are at very high risk 1
Some research suggests that an HbA1c cutoff point of 5.9% may better identify individuals at high risk of progression to diabetes than the 5.7% value in certain populations 4
The positive predictive value of HbA1c for diagnosis of prediabetes in clinical practice may be limited, with some studies showing values as low as 39.4% 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) with one or more 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 minimum 3-year intervals is reasonable 1

Individuals with HbA1c of 5.7-6.4% should be informed of their increased risk for diabetes and cardiovascular disease 1
Lifestyle modification (calorie restriction, increased physical activity ≥150 min/week) has been shown to decrease the incidence of diabetes by 6.2 cases per 100 person-years over a 3-year period 2
Metformin may be particularly effective for women with prior gestational diabetes and individuals younger than 60 years with BMI ≥35, fasting plasma glucose ≥110 mg/dL, or HbA1c ≥6.0% 2