Specimen Requirements

Patient Preparation1. Patient should not be receiving intravenous glucose.
2. Patient should be on at least a 150 g carbohydrate diet for 3 days prior to testing and should be off all hypoglycemic drugs, such as birth control pills, aspirin, diuretics, ethanol, and steroids.
3. The patient should not have any acute illness or other stress at the time of the test.
4. Ideally, the test should not be performed on hospitalized patients.
5. Test should begin at 7 a.m. to 9 a.m. after a 16 to 18 hour fast, although water is allowed.
6. Patient should remain quiet during test, taking no food or drugs.
7. If diarrhea or vomiting occurs, the test is aborted, and should be done another day.

Specimen Collection
Draw blood in a grey-top (potassium oxalate/sodium fluoride) tube(s) from a fasting patient. Spin down and send 1 mL of potassium oxalate/sodium fluoride plasma. Collect specimen as follows:
1. A fasting glucose is drawn in a grey-top (potassium oxalate/sodium fluoride) tube(s). Label tube with appropriate patient information, date and time, and “fasting.”
2. Patient is given a 75 g dose of glucose. Ten ounce bottles of tolerance beverage contain 100 g. Patients will need to drink 225 mL. Measure and discard 75 mL. Pregnant patients receive 100 g—the whole bottle. Instruct patient to drink the whole amount within several minutes. Note the time when the patient has finished. All drawing times are calculated from finish time.
3. A grey-top (potassium oxalate/sodium fluoride) tube is drawn for each specimen, fasting, 1/2 hour, 1 hour, 2 hours, etc. Physicians may order from a 2-hour up to a 6-hour tolerance.
4. Patients should remain fasting; only water is permitted.
5. Smoking is not acceptable during test.