Pre-Diabetes A1C Level
Pre-diabetes is defined as an A1C level between 5.7% and 6.4% (39-47 mmol/mol), which identifies individuals at substantially increased risk for developing type 2 diabetes and cardiovascular disease. 1
Diagnostic Criteria
The American Diabetes Association establishes three diagnostic criteria for pre-diabetes, any one of which qualifies for the diagnosis: 1, 2
- 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)
A1C testing must be performed using a method certified by the National Glycohemoglobin Standardization Program (NGSP) in an accredited laboratory. 2
Risk Stratification Within the Pre-Diabetes Range
The pre-diabetes A1C range represents a continuum of risk that increases disproportionately as A1C rises, not a uniform risk category. 1
- A1C 5.7-6.0%: Moderate risk with 9-25% 5-year diabetes incidence 3
- A1C 6.0-6.4%: Very high risk with 25-50% 5-year diabetes incidence, representing a 20-fold increased risk compared to A1C of 5.0% 1, 3
- A1C >6.0%: Should trigger aggressive interventions and particularly vigilant follow-up 1
The relationship between A1C and diabetes risk is curvilinear—as A1C rises from 5.0% to 6.5%, risk increases steeply rather than linearly. 4
Management Strategies
First-Line: Intensive Lifestyle Modification
All individuals with pre-diabetes should be referred to an intensive behavioral lifestyle program as first-line therapy. 5, 2
The target goals include: 5, 6
- Weight loss: 7% of initial body weight
- Physical activity: At least 150 minutes per week of moderate-intensity exercise (such as brisk walking)
- Dietary modification: Reduced-calorie meal plan with various eating patterns acceptable 1
Intensive lifestyle intervention reduces diabetes incidence by 6.2 cases per 100 person-years over 3 years (58% relative risk reduction), with sustained long-term benefits including 43% reduction at 20 years and 34% reduction at 10 years. 5, 6
Pharmacologic Therapy: Metformin
Metformin should be considered for very high-risk individuals who meet specific criteria, not for all persons with pre-diabetes. 5, 2
Consider metformin for individuals with: 5, 2, 6
- BMI ≥35 kg/m²
- Age <60 years
- History of gestational diabetes
- A1C ≥6.0%
- Fasting plasma glucose ≥110 mg/dL
Metformin reduces diabetes incidence by 3.2 cases per 100 person-years over 3 years (31% relative risk reduction), which is less effective than lifestyle modification but provides an important adjunctive option for high-risk patients. 6
Monitoring and Follow-Up
At least annual monitoring for progression to diabetes is recommended for all individuals with pre-diabetes. 1, 2
- For A1C >6.0%: More intensive follow-up should be pursued given the very high risk 1, 2
- Initial reassessment: Recheck A1C in 3 months to assess response to lifestyle changes 5
- If not progressing: Repeat testing at minimum 3-year intervals is reasonable 2
- Cardiovascular risk factors: Screen for and aggressively treat hypertension, dyslipidemia, and smoking 2
Important Clinical Caveats
A1C may be problematic for diagnosis in certain populations and should be interpreted with caution. 1
- Hemoglobinopathies and conditions affecting red blood cell turnover can falsely alter A1C values 1
- Low positive predictive value: One study found that only 39.4% of patients with A1C-based pre-diabetes had confirmed dysglycemia on oral glucose tolerance testing 7
- Risk exists below 5.7%: Individuals with A1C below 5.7% may still be at risk depending on the specific A1C level and presence of other risk factors such as obesity and family history 1, 4
Pre-diabetes increases cardiovascular disease risk independent of diabetes progression, making cardiovascular risk factor management essential even if diabetes does not develop. 2, 6