Glucose Tolerance

Source	Blood
Mnemonic	non-pregnant: GTTNP pregnant: GTTP
Specimen Requirements	Test cannot be collected by Mobile Collection Service (MCS). By appointment only. Community patients: contact CLS Patient Appointment Line at 403-777-5136 to book an appointment at any Patient Service Centre. Hospital patients: nursing unit to book appointment with on site lab. After collection of a fasting specimen, a glucose tolerance drink is given to the patient, followed by subsequent blood glucose testing. Patients weighing less than 43 kg (92 lb) are given a 1.75g dose/kg body weight, up to a 75g maximum dose. 1 x 3 mL or 4.5 mL light green (mint) top PST tube. Gold top SST tube also acceptable. 0.2 mL heparinized plasma or serum Pediatric: 0.2 mL whole blood Patient MUST be fasting
Specimen Handling
Additional Information	PSC: Patient instruction sheet (form #CH3002) may be given to patient. Procedure takes 2 or more hours. If fasting glucose value is over 7.8 mmol/L (when tested by glucose meter) or over 7.0 mmol/L (serum or plasma tested by Chemistry department), the patient's ordering physician will be contacted and the test may be cancelled. For Diabetes Clinical Practice Guidelines, please see: Canadian Diabetes Assn. 2008 C.P.G. The drink provided for this test includes the following ingredients: Glucose Citric acid FD&C Yellow #6 Natural flavours Pure water Sodium benzoate
Testing Location	Chemistry-ACH, DSC, FMC, PLC & RGH
Testing Frequency	Weekdays
Alternate Name(s)
Reference Interval	Reference Interval Fasting Specimen: 3.9-6.1 mmol/L Interpretation Non-Pregnant Adults: If fasting glucose greater or equal to 7.0 mmol/L or 2 h PC greater or equal to 11.1 mmol/L, diagnostic of diabetes mellitus. If fasting glucose is 6.1 to 6.9 mmol/L and 2 h PC between 7.8 and 11.0 mmol/L, indicates impaired glucose tolerance. Children <17y: The diagnostic criteria for diabetes in children are the same as for adults. Pregnant: Screen: Test should be performed between 24-28 weeks gestation. A glucose tolerance test is warranted if the 1 hour glucose value is 7.8-10.2 mmol/L. Gestational diabetes mellitus is diagnosed if the 1 hour glucose value is greater than or equal to 10.3 mmol/L. Please see the Canadian Diabetes Association 2008 Practice Guidelines. Tolerance: Gestational Diabetes Mellitus is diagnosed when at least 2 of the following values on the glucose tolerance test are met or exceeded. If 1 value is met or exceeded, a diagnosis of impaired glucose tolerance of pregnancy is established. - Fasting glucose > 5.3 mmol/L - 1 hour glucose > 10.6 mmol/L - 2 hour glucose > 8.9 mmol/L Hypoglycemia: Documentation of reactive hypoglycemia requires demonstration of Whipple’s Triad: Symptoms Alleviation by glucose Plasma glucose less than 2.8 mmol/L