how is diabetes mellitus diagnosed
Asked by: HealthCurious
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Community Answer
Answered by Dr. Emily Carter, MD
Diabetes mellitus is typically diagnosed through several blood tests that measure blood glucose levels. The most common tests include:
- Fasting Plasma Glucose (FPG) Test: Measures blood sugar after an overnight fast. A level of 126 mg/dL or higher indicates diabetes.
- Oral Glucose Tolerance Test (OGTT): Measures blood sugar before and 2 hours after drinking a glucose-rich drink. A 2-hour level of 200 mg/dL or higher indicates diabetes.
- Hemoglobin A1C Test: Measures average blood sugar levels over the past 2-3 months. An A1C level of 6.5% or higher indicates diabetes.
Diagnostic Criteria
Test Normal Prediabetes Diabetes
FPG <100 mg/dL 100-125 mg/dL ≥126 mg/dL OGTT <140 mg/dL 140-199 mg/dL ≥200 mg/dL A1C <5.7% 5.7%-6.4% ≥6.5%
If you have symptoms of diabetes, such as increased thirst, frequent urination, or unexplained weight loss, a single abnormal test result may be sufficient for diagnosis. Otherwise, a second test is usually required to confirm the diagnosis.