Additional Specimen Instructions

This order profile follows the American Diabetes Association criteria and includes measurement of fasting plasma glucose as well as plasma glucose measurement 2 hours after a 75 gram oral glucose load.

For PEDIATRIC patients the dose of glucose is calculated based on the patient`s body weight measured in kilograms. The appropriate dose is 1.75 grams per kilogram (kg) of body weight to a maximum dose of 75 grams of glucose. (Example: a 40 kg patient should receive a 70 gram dose. 1.75 g x 40 kg = 70 grams).

1.The patient should be fasting (8 to 12 hours) prior to beginning this test. 2.Draw a gray top tube for a fasting plasma glucose concentration. 3.Give the patient the 75 gram glucose drink or lower dose based on body weight for pediatric patients. The glucose drink can be obtained from the laboratory. 4.Instruct the patient to drink the entire volume. 5.Begin timing once the patient has finished the drink. 6.Draw an additional gray top tube 2 hours after the patient has finished the drink. Gray top tubes are preferred for glucose measurement as they contain a glycolytic inhibitor (NaF) that stabilizes the plasma glucose concentration. If the GTT is drawn in conjunction with other plasma chemistry tests a green top plasma separator tube (LiHeparin) is acceptable if the green top tube is centrifuged within 1 hour of collection. All specimens should be collected in the same container type for the duration of the tolerance.