Standard Glucose Tolerance Test: What to Know

You are usually asked to fast beforehand, with the clinic giving exact instructions about food, drinks and medicines. A blood sample is taken, you drink a glucose solution, and another sample is collected after the specified waiting period. Remain seated and avoid eating, strenuous activity and unapproved drinks during the test because these can affect the result. You may feel briefly nauseated, light-headed or uncomfortable after the drink.

The result is interpreted against the laboratory or maternity service thresholds used for your care. An abnormal result does not explain its cause by itself; your clinician will discuss whether further assessment, monitoring or treatment is needed.

Confirm when fasting begins and whether you should take regular medicines. Bring water if the clinic allows it, something to eat for afterward, and a way to pass the waiting time. Tell staff if you vomit, feel unwell, cannot complete the drink or accidentally eat during the appointment; the test may need to be rearranged. Keep usual meals and activity before the fasting period unless your maternity team gives different instructions.

Attend the appointment arranged as part of antenatal care. If a result needs action, ask how to monitor glucose, plan meals and recognise symptoms that require advice.

Contact your maternity team if you cannot keep the drink down, become faint, develop marked weakness or feel confused during or after testing. Seek urgent care for collapse, severe breathing difficulty or a rapidly worsening condition. After an elevated result, follow the review plan; urgent advice is needed for severe thirst with frequent urination, vomiting, abdominal pain or unusual drowsiness.

Ask: How long should I fast? Can I take my regular medicines? What happens if I vomit? When will the result be available? What does an abnormal result mean for monitoring during pregnancy and after birth?