Fasting plasma glucose (FPG), two-hour plasma glucose during a 75 g oral glucose tolerance test (OGTT), or glycated hemoglobin (A1C) may be used for diagnostic testing.
Symptomatic hyperglycemia — The diagnosis of diabetes mellitus is easily established when a patient presents with classic symptoms of hyperglycemia (thirst, polyuria, weight loss, blurry vision) and has a random blood glucose value of 200 mg/dL (11.1 mmol/L) or higher. Most patients with type 1 diabetes are symptomatic and have plasma glucose concentrations well above ≥200 mg/dL. Some patients with type 2 diabetes also present with symptomatic hyperglycemia and blood glucose ≥200 mg/dL.
|American Diabetes Association criteria for the diagnosis of diabetes
|1.||A1C ≥6.5%. The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay.
|2.||FPG ≥126 mg/dL (7 mmol/L). Fasting is defined as no caloric intake for at least 8 hours.
|3.||2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during an OGTT. The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.
|4.||In a patient with classic symptoms of hyperglycemia or hyperglycemic crisis, a random plasma glucose ≥200 mg/dL (11.1 mmol/L).|
Asymptomatic hyperglycemia — The diagnosis of diabetes in an asymptomatic individual (generally type 2 diabetes) can be established with any of the following criteria:-
The ADA criteria to diagnose prediabetes are as follows: –
|Categories of increased risk for diabetes (prediabetes)|
|1.||FPG 100 to 125 mg/dL (5.6 to 6.9 mmol/L) – IFG|
|2.||2-hour post-load glucose on the 75 g OGTT 140 to 199 mg/dL (7.8 to 11.0 mmol/L) – I|
|3.||A1C 5.7 to 6.4% (39 to 46 mmol/mol)|