A1C Diagnostic Threshold for Diabetes

Diagnostic Categories

• The American Diabetes Association recommends an A1C level of 6.5% or higher as the diagnostic threshold for diabetes, with a specificity of 98% for detecting diabetes 1, 2
• The American Diabetes Association has established clear A1C-based diagnostic categories, where A1C ≥6.5% confirms diabetes 1, 2
• The diagnostic threshold of 6.5% was established based on the glycemic level at which retinopathy prevalence begins to increase in a linear fashion 1

Prediabetes and Normal Range

• The American Diabetes Association defines prediabetes as an A1C range of 5.7-6.4%, which identifies individuals at substantially increased risk for future diabetes and cardiovascular disease 2, 3
• An A1C level of less than 5.7% is considered normal, but risk exists on a continuum even below 5.7%, particularly with additional risk factors like obesity and family history 2, 3

Clinical Application Considerations

• The relationship between A1C and diabetes risk is curvilinear, not linear, with risk increasing steeply as A1C rises from 5.0% to 6.5% 1, 2
• Individuals with A1C 6.0-6.4% have a relative risk 20 times higher than those with A1C 5.0% 3
• A1C should be measured using a method certified by the National Glycohemoglobin Standardization Program (NGSP) to ensure accuracy 1