Test Name: Glucose Tolerance Test 
Alternate Test Names GTT; OGTT; Oral Glucose Tolerance test 
PLS Test Code GTT  Laboratory Biochemistry 
Specimen Blood (X 3)  Analysis Performed On Plasma 
Container Fluoride oxalate Tube 2 ml  Container colour Grey 
Multiple specimens . Three timed specimens are required 
Required Volume Adult (mL) 2  Req Vol Paediatric (mL) 2 
Reference Ranges  
Turnaround Time Routine 8 Hours  Turnaround Time Urgent  
Turnaround Other  
Days test is performed Daily  Transport Room temperature 
Special Requirements NB: Some clinicians request GTT & insulin levels, in which case a lithum heparin tube (on ice) must be collected at 0, 1 and 2 hours. Test should be performed in the morning (started before 10.00 am). GTTs are rarely indicatd for children under 14 years of age. If requested please contact a senior staff member in Clinical Biochemistry on 9288 4112 before proceeding. If a GTT is done on a child the dose glucose dose is 1.75 g/kg up to 75 g. 
Patient Preparation 1. Three days of normal carbohydrate diet. 2. Overnight fast, nothing to eat or drink and no smoking for 10 hours prior to test, water allowed. 3. No current illness (eg infection) or stresses (eg recent surgury or trauma) that might invalidate test. 
Collection Instructions Blood glucose levels should be checked using a glucose meter prior to glucose administration. The result must be recorded on request form on the labels available from stores. If fasting glucose is higher than 8.5 mmol/l consult with patient's doctor to ensure it is safe to continue. If the test is cancelled due to the high fasting glucose collect only the fasting specimen. Patient must be seated quietly for 30 minutes prior to and during the test. Patient must not smoke, eat or drink during the test. 1. Collect fasting blood by venepuncture. Label tube with Surname, First name, D.O.B., date and time of collection and "FASTING". 2. Administer 75gms glucose drink to patient. (Use only glucose drink from St. Vincent's Pathology Stores Department). Glucose drink must be completed within 10 minutes. 3. Collect 1st hour specimen by venepuncture 1 hour after the COMPLETION of the glucose drink. Label tube with surname, first name, D.O.B., date and time of collection and "1st HOUR". 4. Collect 2nd hour specimen by venepuncture 2 hours after COMPLETION of the glucose drink. Label tube with surname, first name, D.O.B., date and time of collection and "2ND HOUR". 
Clinical Information If the patient is pregnant this must be unequivocally indicated on the request form. 
Sent to Reference Laboratory No 
Ref Laboratory Name  
Estimated Patient Fee N/A 
Last Updated 25-Aug-2006 (Version: 1.00)