From the Guidelines
The diagnostic criteria for Type 2 Diabetes Mellitus (DM2) include any one of the following: a fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher on two separate occasions, 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 a patient with classic symptoms of hyperglycemia, or a hemoglobin A1C level of 6.5% or higher, as recommended by the most recent guidelines 1.
Diagnostic Thresholds
The diagnostic thresholds are based on the correlation between glucose levels and risk of microvascular complications, particularly retinopathy.
- Fasting plasma glucose: 126 mg/dL (7.0 mmol/L) or higher
- 2-hour plasma glucose during an oral glucose tolerance test: 200 mg/dL (11.1 mmol/L) or higher
- Random plasma glucose in a patient with classic symptoms of hyperglycemia: 200 mg/dL or higher
- Hemoglobin A1C: 6.5% or higher
Prediabetes Diagnosis
Prediabetes is diagnosed when:
- Fasting glucose is between 100-125 mg/dL (impaired fasting glucose)
- 2-hour glucose during OGTT is between 140-199 mg/dL (impaired glucose tolerance)
- A1C is between 5.7-6.4%
Importance of Early Diagnosis
Early diagnosis is crucial as many patients have had diabetes for years before diagnosis and may already have complications. Risk factors that should prompt screening include:
- Obesity
- Family history of diabetes
- Certain ethnicities
- History of gestational diabetes
- Age over 45 years
Screening Recommendations
Screening for prediabetes and type 2 diabetes risk through an informal assessment of risk factors or with an assessment tool, such as the ADA risk test, is recommended to guide providers on whether performing a diagnostic test is appropriate, as stated in the guidelines 1.
The most recent study 1 provides the most up-to-date recommendations for the diagnosis of type 2 diabetes, and its findings should be prioritized in clinical practice.
From the Research
Diagnostic Criteria for Diabetes Mellitus (DM) Type 2
The diagnostic criteria for Diabetes Mellitus (DM) type 2 include:
- Fasting plasma glucose (FPG) levels of 7.0 mmol/L or higher (126 mg/dL or higher) 2, 3, 4
- Glycated hemoglobin (HbA1c) levels of 6.5% or higher 3, 4, 5
- 2-hour plasma glucose levels of 200 mg/dL or higher during an oral glucose tolerance test (OGTT) 3, 6
Classification of Glucose Levels
The classification of glucose levels is as follows:
- Normal: FPG < 6.1 mmol/L (110 mg/dL) and HbA1c < 6.5% 2, 3
- Impaired fasting glucose (IFG): FPG 6.1-6.9 mmol/L (110-125 mg/dL) 2, 3
- Diabetes: FPG ≥ 7.0 mmol/L (126 mg/dL) or HbA1c ≥ 6.5% 2, 3, 4
Diagnostic Approach
The diagnostic approach for DM type 2 involves: