If a fasting glucose was 90 mg/dL, which 2 hour postprandial glucose result would most closely represent normal glucose metabolism?

• A. 55 mg/dL (3.0 mmol/L)
• B. 100 mg/dL (5.5 mmol/L)
• C. 180 mg/dL (9.9 mmol/L)
• D. 260 mg/dL (14.3 mmol/L)

Answer: (B)

On normal glucose metabolism after a meal, glucose rises only modestly and should return toward baseline within about two hours. The 2-hour postprandial value shows how well insulin is handling the glucose load. With a fasting glucose of 90 mg/dL, a 2-hour value around 100 mg/dL fits the normal range, since normal postprandial glucose is generally under about 140 mg/dL.

A value of 55 mg/dL would be too low after a meal (hypoglycemia), not normal. A value of 180 mg/dL is elevated and indicates impaired glucose tolerance rather than normal metabolism, and 260 mg/dL is clearly in the diabetic range. Therefore, the 2-hour postprandial glucose around 100 mg/dL best represents normal metabolism.