The OGTT criterion for diabetes is a 2-hour plasma glucose greater than 200 mg/dL.

• A. 2-hour plasma glucose >200 mg/dL
• B. Fasting plasma glucose >126 mg/dL
• C. A1c >6.5%
• D. Random plasma glucose >200 mg/dL

Answer: (A)

The test value being described is the post-load measurement that the oral glucose tolerance test uses. After a person who has fasted drinks a standard glucose load (about 75 g), blood glucose is checked two hours later. If that two-hour plasma glucose is greater than 200 mg/dL, it meets the diagnostic threshold for diabetes on the OGTT. This post-load spike shows how well the body handles a glucose challenge, revealing diabetes even when fasting glucose might seem normal. Other criteria for diagnosing diabetes rely on different measurements—fasting plasma glucose of 126 mg/dL or higher, or an HbA1c of 6.5% or higher, or a random glucose of 200 mg/dL or higher only when hyperglycemia symptoms are present. The OGTT criterion specifically uses the two-hour value after the glucose load.