If your healthcare team feel it’s important to test you for gestational diabetes, you’ll normally be tested between 24 and 28 weeks of pregnancy, although you might test earlier if you’re at higher risk of developing it or have had it before.
What tests tell me I have gestational diabetes?
The main test used to diagnose gestational diabetes is a blood test known as the oral glucose tolerance test (OGTT). This is a simple test that doesn’t harm you or your baby.
Oral glucose tolerance test (OGTT)
The OGTT takes just over two hours to complete and is usually done at the clinic or hospital where you have been receiving antenatal care, or a specialist diabetes clinic.
How does an oral glucose test work?
The test consists of the following steps:
- You'll need to fast (not eat or drink anything except water) for 8-10 hours the night before and the morning of the test.
- You’ll have a blood test to measure your blood glucose level.
- You’ll then be given a glucose (sugary) drink.
- After resting for two hours, you'll have another blood test to see how your body is dealing with the glucose.
You shouldn’t eat anything before or during the gestational diabetes test. But it’s a good idea to bring a snack with you to have afterwards, as you’ll probably be hungry. You can have sips of water to drink before and during the test.
You won’t always receive the tests results on the same day as the test. After the test, you will be diagnosed with gestational diabetes if your fasting blood sugar level is 5.6mmol/l or above or if your 2hr post glucose blood sugar level is 7.8mmol/l or above.
If the test shows you don't have gestational diabetes, it's important to be aware that gestational diabetes can develop at any time. So if you develop any symptoms of gestational diabetes it's important to trust your instincts and tell your healthcare professional about this or anything else you're worried about.
"My midwife referred me to the hospital to do an Oral Glucose Tolerance Test (OGTT). I didn’t think I needed to worry about diabetes as I wasn’t overweight, but my South Asian background was a risk factor for gestational diabetes, which I hadn’t realised up to this point."
Read Reena’s story about gestational diabetes.
How do I prepare for a gestational diabetes test?
Apart from fasting for 8-10 hours before the test, you don’t need to do anything different to prepare for the gestational diabetes test. But check the leaflet you are given about the test so you’re sure what to expect from your clinic.
Is 30 weeks too late for a glucose test?
Testing for gestational diabetes isn’t routinely done at or beyond 28 weeks. If you have any symptoms of gestational diabetes in your pregnancy, speak to your midwife or doctor for advice.
What happens if you are diagnosed with gestational diabetes?
If you're diagnosed with gestational diabetes, you should be referred to your to the joint diabetes and antenatal clinic within one week. and referred to a dietitian. You should receive regular care and support.
They will recommend the best treatment for you and advise you on how you can test your blood sugars at home and follow a healthy diet.
Some women might be able to reach their target blood sugar levels with diet and exercise alone, or you might be prescribed metformin or insulin to help.
Read more about what NHS care you can expect before and after you give birth if you have gestational diabetes, and what treatments for gestational diabetes are available.
Although gestational diabetes usually goes away after you give birth, it leaves you with a high risk of type 2 diabetes. So you'll need NHS follow-on care and support to help you reduce your risk of type 2 diabetes.
Is gestational diabetes my fault?
If you do get diagnosed with gestational diabetes, it’s important to remember it’s not your fault.
You might be feeling shocked or guilty about the diagnosis and wondering if you caused it somehow, but this isn’t the case.
There’s a lot happening in the body during pregnancy. As well as the physical signs, the pregnancy hormones you produce can make it hard for your body to use insulin properly, a hormone that controls blood sugar levels.
Some women’s bodies can’t produce enough insulin to overcome it and meet your extra needs in pregnancy. This can lead to insulin resistance.
This makes it difficult to use glucose (sugar) properly for energy, so it stays in your blood and the sugar levels rise. This then leads to gestational diabetes.
Gestational diabetes and your mental health
During pregnancy, your midwife and care team should ask if you’ve ever had problems with your mental health and check in on whether you’re having any now.
If you’re feeling bad about yourself or experiencing any other symptoms of depression, remember you’re not alone. Don’t be afraid to be open and ask for support. It’s a hard thing to do, but asking for help and talking about how you’re feeling can be really helpful.
“I’d really recommend newly diagnosed mums speak to other mums with, or who’ve had, gestational diabetes, if they can. The moral support really helps.”
– Vicky, a journalist from London
Getting support for mental health
Our helpline is here for you as well as your GP if you want to chat anything through confidentially with a trained advisor or ask questions on 0345 123 2399. You can also reach out for support safely on our forum.
For tips on looking after your mental health and information on further support, go to the NHS mental health problems and pregnancy page.
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