From the Guidelines
The latest criteria for diagnosing diabetes include a fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher, a 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during an oral glucose tolerance test, a random plasma glucose level of 200 mg/dL or higher in patients with classic symptoms of hyperglycemia, or a hemoglobin A1C level of 6.5% or higher, as recommended by the most recent guidelines 1.
Diagnostic Criteria
The diagnostic criteria for diabetes are as follows:
- Fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher
- 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during an oral glucose tolerance test
- Random plasma glucose level of 200 mg/dL or higher in patients with classic symptoms of hyperglycemia
- Hemoglobin A1C level of 6.5% or higher Any one of these criteria can establish the diagnosis if confirmed by repeat testing, though a second test is not needed if the patient has classic symptoms of hyperglycemia with a random glucose above 200 mg/dL 1.
Importance of Early Diagnosis
Early diagnosis is crucial as many patients may have diabetes for years before diagnosis, increasing their risk of complications, such as microvascular complications, particularly retinopathy 1.
Confirmation of Diagnosis
If any one of the criteria is met, confirmation is necessary to establish the diagnosis, which can be accomplished by repeating the same assay on a different blood sample drawn on a subsequent day, or by measuring a different analyte, such as glucose and HbA1c, in samples obtained on the same day 1.
From the Research
Latest Criteria for Diagnosing Diabetes
The latest criteria for diagnosing diabetes include:
- Fasting plasma glucose (FPG) level of 126 mg/dL or higher 2, 3, 4, 5
- 2-hour plasma glucose level of 200 mg/dL or higher during an oral glucose tolerance test (OGTT) 2, 3, 4, 5
- Random plasma glucose level of 200 mg/dL or higher in individuals with classic symptoms of diabetes 3, 6
- Hemoglobin A1C (HbA1C) level of 6.5% or higher 3
Diagnostic Categories
The diagnostic criteria also include the following categories:
- Impaired fasting glucose (IFG): FPG level of 110 mg/dL to 125 mg/dL 2
- Impaired glucose tolerance (IGT): 2-hour plasma glucose level of 140 mg/dL to 199 mg/dL during an OGTT 2
- Gestational diabetes mellitus (GDM): diagnosed using a 100-g, 3-hour OGTT with two or more values exceeding the cutoffs (fasting, 105 mg/dL; 1 hour, 190 mg/dL; 2 hours, 165 mg/dL; 3 hours, 145 mg/dL) 5
Laboratory Diagnosis and Monitoring
Laboratory tests used to diagnose and monitor diabetes include: