An oral glucose tolerance test yields fasting serum glucose of 128 mg/dL and a 2-hour post-load glucose of 238 mg/dL. This result most strongly correlates with which diagnosis?

An oral glucose tolerance test yields fasting serum glucose of 128 mg/dL and a 2-hour post-load glucose of 238 mg/dL. This result most strongly correlates with which diagnosis?

• A. Diabetes Mellitus
• B. Impaired Fasting Glucose
• C. Impaired Glucose Tolerance
• D. Normal Glucose

Answer: (A)

Oral glucose tolerance test interpretation hinges on diagnostic thresholds for diabetes. Diabetes can be diagnosed if fasting glucose is 126 mg/dL or higher, or the 2-hour glucose after a 75 g load is 200 mg/dL or higher. Here, the fasting value is 128 mg/dL and the 2-hour value is 238 mg/dL, both exceeding the diabetes thresholds. This makes diabetes mellitus the best match because two independent criteria are met, not just one in the impaired ranges. Impaired fasting glucose would require fasting in the roughly 100–125 mg/dL range, which isn’t the case here. Impaired glucose tolerance would involve a 2-hour value in the 140–199 mg/dL range, which also isn’t the case since it’s 238 mg/dL. Normal glucose would be fasting below 100 mg/dL and a 2-hour value below 140 mg/dL, which clearly isn’t true either.

Oral glucose tolerance test interpretation hinges on diagnostic thresholds for diabetes. Diabetes can be diagnosed if fasting glucose is 126 mg/dL or higher, or the 2-hour glucose after a 75 g load is 200 mg/dL or higher. Here, the fasting value is 128 mg/dL and the 2-hour value is 238 mg/dL, both exceeding the diabetes thresholds. This makes diabetes mellitus the best match because two independent criteria are met, not just one in the impaired ranges.

Impaired fasting glucose would require fasting in the roughly 100–125 mg/dL range, which isn’t the case here. Impaired glucose tolerance would involve a 2-hour value in the 140–199 mg/dL range, which also isn’t the case since it’s 238 mg/dL. Normal glucose would be fasting below 100 mg/dL and a 2-hour value below 140 mg/dL, which clearly isn’t true either.