Diagnosing gestational diabetes  

Every pregnant woman with one or more risk factors should be offered a screening test for gestational diabetes.

Screening identifies otherwise healthy people who may be at increased risk of a condition, such as diabetes. You can then be offered information and further tests to determine whether you have the condition.


You may be screened for gestational diabetes at your first antenatal appointment with your midwife or GP, which takes place around weeks 8-12 of your pregnancy.

At this time, your GP or midwife will find out if you are at increased risk of gestational diabetes. They will ask about any known risk factors for gestational diabetes, such as whether you have a family history of diabetes.

If any of these risk factors apply to you, you'll be offered a blood test to check your glucose levels. This may also include a glucose tolerance test (GTT).

Glucose tolerance test (GTT)

A GTT takes place during weeks 24-28 of pregnancy.

This involves a morning blood test, before you have eaten breakfast. You are then given a glucose drink, and another blood sample is taken two hours later to see how your body is dealing with the glucose.

If you had gestational diabetes in a previous pregnancy, the GTT will be carried out at weeks 16-18 of pregnancy  or sooner, if indicated by the first blood glucose sample. This is followed by a repeat GTT at 28 weeks, if the first test is normal.

Read more about how gestational diabetes is treated.

Page last reviewed: 07/08/2014

Next review due: 07/08/2016