Normal HbA1c Reference Range in Healthy Non-Pregnant Adults
In healthy non-pregnant adults without diabetes, the normal HbA1c reference range is 4.8–5.6% (29–38 mmol/mol), with values ≥5.7% indicating prediabetes and ≥6.5% indicating diabetes. 1
Defining Normal vs. Prediabetes vs. Diabetes
Normal glycemia: HbA1c <5.7% (39 mmol/mol) represents normal glucose regulation in adults without diabetes 1
Prediabetes threshold: HbA1c 5.7–6.4% (39–46 mmol/mol) defines prediabetes, though some organizations use 6.0–6.4% as the diagnostic range 1
Diabetes diagnosis: HbA1c ≥6.5% (48 mmol/mol) is diagnostic for diabetes 2, 1
Clinical Context for Interpretation
The normal reference range represents the HbA1c distribution in healthy individuals without glucose metabolism disorders. This differs fundamentally from treatment targets in patients with established diabetes, where goals are individualized based on disease duration, complications, and hypoglycemia risk 3.
Key Distinction: Normal Range vs. Treatment Targets
Healthy adults maintain HbA1c levels naturally below 5.7% without intervention 1
Patients with diabetes aim for treatment targets of 6.5–8.0% depending on individual factors—these are therapeutic goals, not "normal" values 3, 2
The gap between normal physiology (<5.7%) and diabetes treatment targets (≥6.5%) reflects the balance between glycemic benefit and treatment-related harms in disease management 3
Important Caveats
Race and Ethnicity Considerations
HbA1c values vary by race and ethnicity independent of actual glycemia, which can affect interpretation of borderline values 3, 4
This variability should be considered when assessing individuals near diagnostic thresholds 3
Pregnancy Exclusion
These reference ranges do NOT apply to pregnant women, who have significantly lower HbA1c values due to physiological changes 5, 6, 7
In healthy pregnant women, normal HbA1c ranges from 4.3–5.7% depending on trimester, with values decreasing in early-to-mid pregnancy 5, 6, 7
Clinical Significance of Prediabetes Range
Individuals with HbA1c 5.7–6.4% progress to diabetes at approximately 10% per year 1
Prediabetes is associated with increased cardiovascular events and mortality (excess absolute risk of 8.75 cardiovascular events per 10,000 person-years) 1
Intensive lifestyle modification reduces diabetes incidence by 6.2 cases per 100 person-years over 3 years in this population 1