Your Glucose Tolerance Test

Your Glucose Tolerance Test (for Pregnancy and the Postnatal Period)

Patient Information

Maternity Services

• Author ID: JW
• Leaflet Ref: Obs 049
• Version: 5
• Leaflet title: Your Glucose Tolerance Test (for Pregnancy and the Postnatal Period)
• Last Review: May 2021
• Expiry Date: May 2023

What is it?

A glucose tolerance test (GTT) is a test carried out at around 28 weeks of pregnancy to find out if you have gestational diabetes.  This is generally a temporary form of diabetes found in pregnancy causing high levels of glucose in the body especially after food.

Location of test: ……………………………………………………………………………………………………………………

Date: …………………………………………………..   Time:………………………………………………………

Who is at risk?

Those at higher risk of developing gestational diabetes are those who:

• Have had gestational diabetes in a previous pregnancy.
• Have a close family member with type 1 or type 2 diabetes.
• Have previously had a baby which was large for gestational age (LGA). LGA is when a baby’s weight is in the top 10% for babies born at that stage of pregnancy to mothers of a similar size to you.
• Are of an ethnicity with a high prevalence of diabetes in the general population, eg. South Asian, Middle Eastern or Afro-Caribbean origin.
• Are over 38 years old.
• Have a body mass index (BMI) over 30.
• Have been told they have polyhydramnios (extra fluid around the baby).Liquor volume over 10 cm on scan.
• Have had an unexplained stillborn baby in the past.
• Are on antipsychotic medications
• Have polycystic ovaries

What does the test involve?

For 12 hours before the test you should not eat anything or smoke, but you may drink plain water.

Any regular medication in tablet form should be taken as normal with water. Medicines should not be taken as they may contain sugar which could invalidate the test.

The test will take around 2 ½ hours to complete.

On arrival, you will have a urine sample tested, a finger prick blood test and a blood test taken, all of which are to test your glucose levels.

You will then be provided with a glucose drink and asked to drink this in 5 minutes.

You will need to wait in the clinic area for 2 hours, so bring something to keep you occupied as you must stay until the end of the test.  You may not smoke during the test as it will affect the results.

At the end of the 2 hours a final blood test will be taken to complete the test and then you are free to return home or to work. Once the test is over and before you leave, having a snack to eat is a good idea.

The results

The level of glucose in your blood tests tells us if you have gestational diabetes. If your result is positive, you will be contacted within 5 days by a member of the diabetes team and a plan will be made for the rest of your pregnancy.

This plan will include being seen by the diabetes team regularly until your baby is born.

If your test result is negative and your blood glucose levels are normal, you will not be contacted by the diabetes team but, if you wish to know the results ask your community midwife at your next visit.