Glucose Tolerance Test in Pregnancy

Patient Experience

  • Reference Number: HEY-290/2018
  • Departments: Maternity Services
  • Last Updated: 18 July 2018


This leaflet has been produced to give you general information about your procedure.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your midwife and doctor, but may act as a starting point for discussion.   If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team.

What is a glucose tolerance test?

A Glucose Tolerance Test (GTT) is a blood test that is used to diagnose gestational diabetes which can develop during pregnancy. The test measures your body’s ability to maintain a normal blood glucose (sugar) level.

Why do I need a glucose tolerance test?

In pregnancy, women who will be offered a GTT will have been identified as having one of the following:

  • A raised body mass index (BMI) over 30kg/m². BMI is a measurement of your weight in kilograms and your height in metres. (A healthy BMI is below 25kg/m².)
  • A previous baby over 4.5kg (9lbs 14oz).
  • Confirmed gestational diabetes in a previous pregnancy.
  • Family origin (South Asian, Black African, Black Caribbean and Middle Eastern).
  • First degree relative that has diabetes (mother/father/brother/sister).
  • Previous Stillbirth

Can there be any complications or risks?

We would like to reassure you that there is no risk to you or your baby when undertaking the GTT.

How do I prepare for the glucose tolerance test?

Please read the information leaflet. Share the information it contains with your partner and family (if you wish) so that they can be of help and support. There may be information they need to know, especially if they are taking care of you following this examination. If you are taking Metformin for any reason, Please do not take this for 3 days before the test.

Leading up to the test, please continue to eat your normal diet until the night before your test. Please do not restrict your sugar intake.

The night before the test

Do not eat or drink anything other than plain water from 10pm the evening before your test. This includes not eating mints, chewing gum and medication for heart burn.

Please note that if you forget and you eat something in the morning, it is important that you contact the antenatal clinic as your test will have to be rearranged.

What will happen?

You will be given an appointment to attend the Antenatal Clinic at the Women and Children’s Hospital on the Hull Royal Infirmary site or at a Health Centre close to where you live.

When you attend your appointment, you will have a blood sample taken from your arm and will be given a special glucose drink to take. After two hours the blood test will be repeated.

You must not eat anything until after the second blood sample has been taken. Whilst you are waiting for the second blood test, you will have to stay within the department, as too much walking around may affect the results of the test.

Please be aware that we have limited space in the department and as the test takes over two hours to complete, we would appreciate it if you could restrict the number of relatives/friends/children you bring with you.

What happens afterwards?

Following the second sample of blood having been taken, you will be able to eat and drink as normal. Please bring a snack you can eat after the test is completed.

You are able to leave after the second blood sample has been obtained and you are fit and well to leave.


The results of your GTT will be available the following week. A copy of this will go to the Antenatal Clinic to be filed in your hospital records.

  • If the result of your GTT is normal
    The copy of the result stays in your hospital records, however you will not be contacted. Your community midwife may be able to access the results electronically if you request the result. If you have any concerns regarding the test results, please do not hesitate to contact the Antenatal Clinic.
  • If the result of your GTT is abnormal
    You will be offered an appointment at the hospital to discuss the result with a Diabetes Specialist Midwife within 2 weeks of the test. Further appointments will be made for you to be seen at a Consultant clinic that specialises in gestational diabetes.

Useful contact numbers

More information about diabetes and gestational diabetes can be found at:

NHS Choices:

Diabetes UK:

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact the Antenatal Clinic, Women and Children’s Hospital on telephone number (01482) 382623.

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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