At around 26-28 weeks' gestation it is recommended that you have a screening test for Gestational Diabetes (GDM). There are 2 different tests depending on whether you are high risk for GDM.
Glucose Challenge Test (GCT)
This is the basic screening test for those women who are not at high risk of developing diabetes. It is a random non-fasting blood test although we would recommend you have the test done mid morning after a light breakfast or mid afternoon after a light lunch. On arrival at the lab, you will be given a standard sweet glucose drink and then a blood test will be done exactly 1 hour later. Is it required that you stay sitting in the lab for the entire hour. Often you will have some other tests added to the GCT including a blood count and iron level.
If the GCT is normal, it is unlikely you have diabetes. It the GCT is elevated, this does not mean you have diabetes but further testing is required in the form of a Glucose Tolerance Test (see below).
Glucose Tolerance Test (GTT)
This is the definitive test for diabetes. You will be advised to have this test if your GCT is elevated or you have any risk factors for diabetes (family history, previous big baby, high BMI, other medical issues, etc). The GTT is more complex. You will need to fast overnight and arrive at the lab first thing in the morning. A fasting blood test will be taken then you will be given a standard sweet glucose drink. You will have a second blood test collected one hour later, and again 1 hour after that. The entire GTT takes just over 2 hours and you must stay sitting in the lab for the entire time. You may not eat anything, however you can drink water. The results of these blood tests are very specific and, if elevated, indicate that you have gestational diabetes.
Gestational Diabetes (GDM)
If you have GDM, you will be given an appointment to be seen by the Diabetes Educator and Dietician at St John of God Hospital. They will explain the condition in detail and give you a plan of management. This plan will include dietary changes, an exercise regimen and instructions/equipment for you to monitor your sugar levels. You will be in close contact with the Educator for the remainder of the pregnancy in conjunction with your Obstetrician. Rarely will women with GDM require insulin injections to control their sugar levels.