Overview
Diabetes in pregnancy (gestational diabetes)
Gestational diabetes is when you have high blood sugar (glucose) during pregnancy. This type of diabetes usually stops after your baby is born.
Insulin is a hormone (chemical substance) that helps to control the sugar levels in your blood. You get gestational diabetes if your body cannot make enough insulin to meet your extra needs when you're pregnant. As a result, your blood sugar levels rise above normal.
Gestational diabetes can happen at any time when you're pregnant. However, it usually starts in the middle or towards the end of pregnancy.
The screening test to diagnose gestational diabetes is called an oral glucose tolerance test.
If the test shows that you have gestational diabetes, we'll monitor your pregnancy and birth more closely. It's important to control your blood sugar levels to keep you and your baby healthy. This information explains how gestational diabetes can affect your pregnancy and how you can reduce complications.
If you have any questions, please speak to your midwife, GP or diabetes team at the hospital.
Why an oral glucose tolerance test is important
We do an oral glucose tolerance test to check if you have diabetes during pregnancy (gestational diabetes).
It's important to know if you have gestational diabetes, as it could result in your baby growing too big, and cause problems when you're giving birth.
Gestational diabetes can have complications that affect you and your baby during pregnancy and after birth. But you can reduce the risks for you and your baby with the diabetes team's support. You can help to control your blood sugar levels during pregnancy by:
• eating a healthy, balanced diet
• keeping active
• taking diabetes medicines, if needed
If gestational diabetes is diagnosed early and well managed, it will help to keep you and your baby healthy.
Who needs an oral glucose tolerance test
You will be referred for an oral glucose tolerance test if 1 or more things (risk factors) make you more likely to get gestational diabetes. These risk factors include:
- a strong history of diabetes in close family members (for example, parents, brothers or sisters)
- previously having gestational diabetes
- previously having a large baby
- when you keep getting sugar (glucose) in your pee (urine)
- being overweight or obese (very overweight with a lot of body fat)
- having too much fluid around your baby in the womb (polyhydramnios)
- previously having shoulder dystocia (when the baby's shoulder gets stuck during birth)
- previously having a baby who died during pregnancy or up to 1 year after birth
- having a south Asian, Black, African-Caribbean or Middle Eastern family background (even if you were born in the UK)
- if you're having a multiple pregnancy
- if you're taking certain medicines
- if you have polycystic ovary syndrome (PCOS)
Preparing for the test
Do
- bring your regular medicines and maternity book with you to the hospital
- bring something to keep you occupied while you are resting during the test (please bring headphones so that you do not disturb other patients)
Don't
- do not eat or drink anything (except water) from 10pm on the night before your test
- do not take any medicines on the morning of the test
What happens during the test
An oral glucose tolerance test includes the following stages:
- We take a small sample of blood soon after you arrive.
- We give you a sugary (glucose) drink.
- We ask you to rest in the waiting area and avoid walking around as much as possible.
- We take a second blood test 2 hours after your first blood test.
In total, you're in the hospital department for about 3 hours. After your second blood test, you can:
- immediately leave hospital
- eat and drink
- take your usual medicines
Risks of an oral glucose tolerance test
Some people feel sick (nausea) and cannot tolerate a sweet drink while they're pregnant. If you cannot manage all of the sugary drink, we can book your oral glucose tolerance test for another date.
Getting your results
Negative result
If the test shows that you do not have gestational diabetes, the results will be available at your next appointment with your midwife. We do not contact you especially.
Positive result
If the test shows that you have gestational diabetes, we'll contact you within 2 working days. We will then make an appointment for you with the diabetes team.
We have more information about what being diagnosed with gestational diabetes means for you and your pregnancy.
More information and support
NHS
The NHS has information on gestational diabetes, and the screening and treatment for this condition.
Diabetes UK
Diabetes UK has information on gestational diabetes, and can give you guidance and support to manage this condition.
Phone 0345 123 2399 (Monday to Friday, 9am to 6pm)
Email [email protected]
Website www.diabetes.org.uk
Royal College of Obstetricians and Gynaecologists
The Royal College of Obstetricians and Gynaecologists has information about:
- what gestational diabetes is
- how it's diagnosed
- what extra antenatal care you can expect
- what this diagnosis means for you and your baby, now and in the future
National Institute for Health and Care Excellence (NICE)
NICE has published an official guideline on managing diabetes in pregnancy. This guideline aims to improve the diagnosis of gestational diabetes. It is also intended to help people manage their blood sugar levels before and during pregnancy.
Resource number: 4381/VER4
Last reviewed: March 2026
Next review due: March 2029
