ANSWER: D. Patients should be tested in a postprandial state either during the occurrence of spontaneous symptoms or with a mixed meal test. The mixed meal diagnostic test includes a meal consumed at the lab that consists of a specific amount of carbohydrates and protein. The patient consumes the mixed meal, which often causes symptoms of hypoglycemia. Samples are collected for plasma glucose, insulin, C-peptide, and proinsulin prior to ingestion of the mixed meal and every 30 minutes thereafter for 5 hours. If a patient is being tested in a spontaneous symptom state the same samples are drawn every 30 minutes for up to 5 hours after the symptoms occurred.
The actual diagnosis of postprandial hypoglycemia is made with a triad of the following symptoms: hypoglycemic symptoms at the same time as a low plasma glucose concentration (less than 50 mg/dL) measured precisely without a glucose monitor and the relief of these symptoms after the plasma glucose is raised. This triad is often called the Whipple’s triad.