Community Answer

Answered by Dr. Emily Carter, MD

Diabetes mellitus (DM) is typically diagnosed through several blood tests that measure blood glucose levels. Here are the common methods:

1. A1C Test

  • What it measures: Average blood glucose levels over the past 2-3 months.
  • Diagnosis Criteria:
    • Normal: Below 5.7%
    • Prediabetes: 5.7% to 6.4%
    • Diabetes: 6.5% or above

2. Fasting Plasma Glucose (FPG) Test

  • What it measures: Blood glucose after an overnight fast.
  • Diagnosis Criteria:
    • Normal: Less than 100 mg/dL
    • Prediabetes: 100 to 125 mg/dL
    • Diabetes: 126 mg/dL or higher

3. Oral Glucose Tolerance Test (OGTT)

  • What it measures: Blood glucose before and 2 hours after drinking a glucose-rich drink.
  • Diagnosis Criteria:
    • Normal: Less than 140 mg/dL
    • Prediabetes: 140 to 199 mg/dL
    • Diabetes: 200 mg/dL or higher

4. Random Plasma Glucose Test

  • What it measures: Blood glucose at any time, regardless of when you last ate.
  • Diagnosis Criteria:
    • Diabetes: 200 mg/dL or higher (with symptoms like increased thirst, urination, and fatigue)

When to Test

  • Adults over 45: Regular screening is recommended, especially if overweight or with other risk factors.
  • Younger Adults: Test if overweight and have additional risk factors like family history, high blood pressure, or physical inactivity.

Always consult with a healthcare provider for accurate diagnosis and personalized advice.

Last updated: 1/15/2025

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