Diagnosis and Management of Diabetes Based on A1C Levels

Diagnostic Criteria

The American Diabetes Association recommends diagnosing diabetes with an A1C ≥ 6.5% (when performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay) 1, 2
Fasting plasma glucose (FPG) ≥ 126 mg/dL after at least 8 hours of fasting is also a diagnostic criterion for diabetes 1
A 2-hour plasma glucose ≥ 200 mg/dL during an oral glucose tolerance test (OGTT) is another diagnostic criterion for diabetes 1
Random plasma glucose ≥ 200 mg/dL in a patient with classic symptoms of hyperglycemia or hyperglycemic crisis is also diagnostic for diabetes 1

An A1C of 10% indicates chronic hyperglycemia over the previous 2-3 months 3
The American Diabetes Association notes that A1C may be affected by hemoglobinopathies, certain anemias, and conditions with abnormal red blood cell turnover 1, 5
In cases of hemoglobinopathies with normal red cell turnover, an A1C assay without interference from abnormal hemoglobins should be used 3, 5
For conditions with abnormal red cell turnover, glucose criteria should be used exclusively for diagnosis 1, 3

An A1C of 10% indicates poor glycemic control if the patient has known diabetes 4
The American Diabetes Association recommends prompt initiation of treatment if newly diagnosed with an A1C of 10% 4
An A1C of 10% is associated with an increased risk for microvascular complications (retinopathy, nephropathy, neuropathy) 3
Comprehensive diabetes management including lifestyle modifications and likely pharmacological intervention is necessary for patients with an A1C of 10% 4