Your glucose tolerance test

Illustration of a pregnant lady and a doctor A glucose tolerance test is a screening test to diagnose gestational diabetes that will be explained to you at your appointment by either your community midwife or when you attend the antenatal clinic if you are booked under consultant-led care.

Preparing for your test

Please ensure you have a good evening meal the night before your test, including rice, pasta, potato or bread. The test is usually done in the morning and you must not eat anything overnight, starting from 10 - 12 hours before your test". You may drink water freely. Smoking can also change the result so please do not smoke after 9.00pm until after the test is finished.

How the test works

The first blood sample will be taken from your arm and you will then be asked to drink a glucose (sugary) drink within five minutes. Following this, you will be asked to sit for two hours in our waiting room and you will be asked not to eat, drink or smoke during this time. You may wish to bring a book or a magazine to keep you entertained and pass the time. After the two hours are completed, we’ll take a second blood sample and you can then go home.

What happens after the test?

If you test positive for gestational diabetes, you will receive a telephone call from one of our diabetes specialist midwives, ideally on the same day that you had your test. Please ensure you leave a current contact telephone number with the maternity assistant and if we cannot contact you by telephone we will leave you a message asking you to get in touch. Please get in touch with us as soon as you receive the message so that we can talk to you about your result, discuss any concerns you may have and arrange an appointment in one of the Diabetes Clinics.

What happens if you are diagnosed with gestational diabetes?

If you’re diagnosed with gestational diabetes you’ll be offered your first appointment with us for a Tuesday morning, Wednesday afternoon or Friday morning. Your care might continue in our Friday clinic or you might be transferred to the consultant clinic on a Tuesday morning.

We also have a group education clinic on a Wednesday afternoon that is a dedicated space for you to meet other women recently diagnosed in a relaxed environment to support you in self-managing gestational diabetes.

We also provide joint follow-up appointments for women with gestational diabetes, if you were booked as low risk in pregnancy, but then develop gestational diabetes during your pregnancy, providing the growth of your baby remains normal and there are no other complications. If further complications arise during your pregnancy, we will discuss and advise transfer of care to the Consultant Diabetes Clinic on a Tuesday.


Unfortunately, we are unable to accommodate partners and children in the GTT waiting room and due to the nature and length of the appointment, we ask that they do not attend. We apologise for any inconvenience this may cause.