Gestational diabetes screening: Preparing for the Recommended Test

Gestational diabetes often causes no symptoms, so feeling well does not tell you whether testing is needed. Your maternity team uses your history and local screening pathway to decide what to offer. The purpose is to identify high blood glucose and arrange care that reduces risks for you and your baby.

Confirm the test and timing

In the NHS pathway, an oral glucose tolerance test is commonly offered between 24 and 28 weeks when risk factors are present. Previous gestational diabetes can mean earlier testing, with another test later if the first is normal. Other countries and services may use different screening steps.

Ask for the full name of your test. Instructions for one type of glucose screening should not be substituted for another. Tell the team if you have had stomach or weight loss surgery, cannot tolerate a glucose drink or have been significantly unwell, so they can decide how to assess you.

Follow your appointment instructions

An oral glucose tolerance test usually requires fasting beforehand. Your clinic should tell you when to stop eating, what you may drink and how to handle your regular medicines. Clarify this in advance rather than stopping essential treatment on your own.

Continue your usual diet in the days before the test unless your team gives different instructions. Restricting sugar to try to improve the result does not help the test answer its intended question. If you accidentally eat during the fasting period, tell the clinic; the appointment may need rearranging.

Bring your maternity notes, medicine list and something quiet to do while waiting. Check how long you need to remain in the department and plan work or childcare accordingly. A snack for after the completed test may be useful.

What happens during the appointment

For the usual NHS oral glucose tolerance test, staff take a fasting blood sample, give a measured glucose drink and take another sample after two hours. You will be asked to rest and follow instructions about food, drinks and movement during the wait.

Tell staff if you feel faint, vomit or cannot finish the drink. They need to know before interpreting the test and can arrange the next step. Do not replace the prescribed drink with a homemade alternative.

Know how the result will reach you

Ask when the result is expected and whom to contact if you have not heard. A result showing gestational diabetes leads to a care discussion, not a judgement about what you ate.

The gestational diabetes care article explains monitoring and treatment after diagnosis. Use the prenatal appointment guide to keep the testing and review dates together, particularly if the test has to be repeated or rearranged.