Glucose Challenge Test (GCT)

Why is it important

This test is performed to screen for diabetes in pregnancy which is called gestational diabetes (GDM). It is important to diagnose GDM in pregnancy because untreated diabetes can harm the health of mother and baby. It is a measure of how your body processes sugar.

What is it?

You are given a very sweet glucose drink and to check your blood glucose level a blood test is performed one hour later. The test is performed at a pathology collection centre. During this hour you cannot eat or drink. Fasting is not necessary, however, it is not advisable to have large amounts of glucose before the test.

What if I have an abnormal GCT result?

If your GCT is abnormal ie. high blood glucose level, you will be contacted and will be required to have a Glucose Tolerance Test (GTT). This will determine if you have gestational diabetes. 20% of all glucose challenge tests will be abnormal but most of these women will not have GDM.

What is a Glucose Tolerance Test (GTT)?

GTT is a fasting test, performed over two hours. You need to fast from midnight and attend a pathology collection centre in the morning. A fasting blood sample will be taken followed by a glucose drink. A second blood sample will be taken in two hours. No food or drink can be consumed during this time. Gestational diabetes is diagnosed if either of these levels are elevated.

What happens if you have gestational diabetes?

If you have gestational diabetes, you will be referred to a diabetes educator and possibly a diabetes specialist (Endocrinologist), and a dietician. These are in addition to your regular obstetric reviews. You will be taught how to monitor blood glucose levels regularly. Most women manage GDM with diet and exercise but in some cases insulin may be required.

Further ultrasounds and other monitoring of the baby may be required later in the pregnancy. Timing and mode of your delivery will depend on multiple factors, including your glucose levels and wellbeing of your baby.

More information is available about Gestational Diabetes.