Tommy's PregnancyHub

Testing for gestational diabetes

If you are at risk of developing gestational diabetes, you’ll usually be offered an oral glucose tolerance test (OGTT).

There are some risk factors that increase your chance of developing gestational diabetes. Your midwife will ask you about these at your booking appointment, which happens around 8-12 weeks of pregnancy. If you have any of the risk factors, you’ll be offered a test for gestational diabetes when you're between 24 and 28 weeks pregnant.

Gestational diabetes does not usually cause any symptoms, but some women may have some if their blood glucose levels get too high. Speak to your midwife if you have any concerns. Talk to your midwife if you think you are at risk of developing gestational diabetes, but you haven’t been offered a screening test.

You don’t have to take the test if it’s offered, but there are a few things to keep in mind:

"I wasn’t obviously skinny, but I wasn’t massively obese either… I had no symptoms whatsoever. I had no expectation that the test would be anything other than a formality."

Beth, mum of two

If you’ve had gestational diabetes before

You will be offered a choice of the following 2 tests to see if you have it again:

  • a kit you can use to check your own blood glucose levels from early pregnancy
  • an oral glucose tolerance test (OGTT), which you will have as soon as possible after your booking appointment, and again at 24-28 weeks if the first test is normal.

What is the oral glucose tolerance test (OGTT)?

Gestational diabetes is tested with the oral glucose tolerance test (OGTT). The test is simple and will not harm you or your baby. It may be carried out at your usual clinic or at a special diabetes clinic.

Step 1 You will usually be asked not to eat anything and drink only water the night before and on the morning of the test.

Step 2 A nurse takes a blood sample from you to measure your blood glucose level.

Step 3 You drink a glucose (sugary) drink.

Step 4 After 2 hours, the nurse takes another blood sample and measures your blood glucose level, to see how your body processed the sugars in the glucose drink.

You shouldn’t eat anything before or during the glucose tolerance test. But if you don’t live near the clinic it’s a good idea to bring a snack with you, as you will probably be hungry afterwards.

After the test

Gestational diabetes can develop at any time during pregnancy. So even if the OGTT shows that you don’t have gestational diabetes, talk to your midwife if you go on to develop any symptoms. It’s important to trust your instincts and tell your health professional if there is anything that you are worried about.

NICE (2015). Diabetes in pregnancy: management from preconception to the postnatal period. National Institute for health and care excellence

Review dates
Reviewed: 23 July 2020
Next review: 23 July 2023

This content is currently being reviewed by our team. Updated information will be coming soon.