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Laboratory Test Reference Guide

Laboratory Information

Test Name

Glucose Tolerance Test (Gestational)


Gestational GTT
GTT Gestational

Specimen Collection

Pre Testing Requirements

For three days prior to the test, the patient must be on a diet containing no less than 150 g of carbohydrate daily. Do not perform this test on an acutely unwell patient or when known to be diabetic. The patient must have fasted for at least 8 hours. GTT should be performed in the morning because fasting glucose levels decrease during the day. Laboratory Phlebotomists carry out this test. Bookings for tests at Waikato Hospital should be made in advance by paging Phlebotomists directly.

Specimen Collection and Transport Protocols

The patient must be at rest and not smoke during the procedure.  The glucose polymer solution ( = 75 g glucose) for this test should be obtained from the pharmacy if not available in your area. 

Adult Specimen

2mL blood, fluoride tube taken at the following intervals:Fasting pre-dose and 2 hours post dose

Test Information



Test Availability

Mon - Fri, 0800 - 1630 excl. Public Holidays


Cobas Pro

Unit of measurement


Reference interval


Gestational diabetes is diagnosed when: fasting glucose > 5.4 mmol/L and/or 2 hour  glucose  > 8.9 mmol/L


Additional Information