What is it?

An oral glucose tolerance test, or OGTT, is a test that looks at the amount of glucose (sugar) in your blood. The results of the test will reveal whether you have gestational diabetes, which is diabetes that develops during pregnancy.

All pregnant women have to complete an OGTT during their pregnancy. This usually happens around 24 - 28 weeks.

Some women who are more at risk of having gestational diabetes need to do an OGTT early in their pregnancy.

You are more at risk if:

  • You’ve had gestational diabetes in a previous pregnancy
  • Your Body Mass Index (BMI) is 30 or above
  • You’re aged over 35
  • You’ve given birth to a baby weighing 4.5kg or more
  • Someone in your immediate family has diabetes
  • You are an Aboriginal or Torres Strait Islander

You can do the test at your medical centre, pathology or local hospital.

 

What do I need to do before the test?

You will usually need to fast the night before the test. Fasting means not eating or drinking anything except water. You can take your usual medicine.

The test takes two-to-three hours, so it’s a good idea to think about what you can take to keep you busy (magazine, book, tablet). You can’t breastfeed during the test, so if you are breastfeeding, make sure you feed before the test begins. You can bring some stored breast milk in case your baby gets hungry.

 

What will happen?

  • A nurse will take a blood sample when you arrive – this measures the ‘resting’ level of sugar in your blood
  • You’ll be given a sweet drink, containing 75g glucose, which tastes like flat lemonade. You will need to drink all of it
  • A nurse will test your blood one and two hours after you drink the sugary drink
  • The whole test may take 2.5 to 3 hours
  • You might feel unwell after the sugary drink – this is normal
  • Your baby may move around more during the test – this is normal
  • You shouldn’t eat or drink until the test is finished

 

What can I expect after?

You will receive the test results within 48 hours. The results show how your body handled the glucose to reveal if you have gestational diabetes. If you test negative, there will be no change to your pregnancy care.

If you test positive, your GP, midwife or obstetrician will talk to you about what that means. You’ll be given help to manage your condition. Your care team may refer you to a specialist clinic to help manage the gestational diabetes.