Prediabetes A1C Range
The prediabetes range for A1C is 5.7% to 6.4% (39-47 mmol/mol), as defined by the American Diabetes Association. 1, 2
Diagnostic Criteria
The American Diabetes Association established three equivalent criteria for diagnosing prediabetes, any one of which qualifies 1:
- A1C: 5.7–6.4% (39–47 mmol/mol)
- Fasting plasma glucose: 100–125 mg/dL (5.6–6.9 mmol/L)
- 2-hour plasma glucose during 75-g OGTT: 140–199 mg/dL (7.8–11.0 mmol/L)
Risk Stratification Within the Prediabetes Range
Risk increases disproportionately at the higher end of the prediabetic range, making the 6.0-6.4% subset particularly concerning. 1, 2
Lower Range (A1C 5.7-6.0%)
- 5-year diabetes incidence: 9-25% 1
- Represents 3- to 8-fold higher risk than the general population 1
- Lifestyle interventions are effective at these levels 2
Upper Range (A1C 6.0-6.4%)
- 5-year diabetes incidence: 25-50% 1
- 20-fold higher relative risk compared to A1C of 5.0% 1
- Requires more intensive interventions and vigilant follow-up 2
- Substantially higher cardiovascular disease risk 3, 4
Clinical Implications
A1C is a stronger predictor of future diabetes and cardiovascular events than fasting glucose in most populations. 1
Key Management Points
- All individuals with A1C 5.7-6.4% should receive counseling about increased diabetes and cardiovascular disease risk 2
- First-line therapy is intensive lifestyle modification: calorie restriction, ≥150 minutes/week physical activity, self-monitoring, and motivational support 3
- Metformin should be considered for highest-risk individuals: women with prior gestational diabetes, age <60 years with BMI ≥35, fasting glucose ≥110 mg/dL, or A1C ≥6.0% 3
- Those with A1C >6.0% warrant particularly intensive intervention and close monitoring 2
Important Caveats
Risk exists on a continuum extending below 5.7%, particularly with additional risk factors like obesity and family history. 5, 6
- The 5.7% cutpoint is somewhat arbitrary—risk increases continuously even at lower levels 1
- Some research questions the positive predictive value of A1C 5.7-6.4% for identifying true glucoregulatory dysfunction, suggesting OGTT confirmation may be warranted in clinical practice 7, 8
- However, the overwhelming guideline consensus and epidemiologic data support the 5.7-6.4% range for clinical decision-making 1, 2
- Baseline BMI and family history of diabetes are critical modifiers of progression risk within the prediabetic range 9