How is a glucose tolerance test done?

The clinic first checks your instructions and takes a blood sample, often after fasting when the test is arranged that way. You then drink a measured glucose solution. Further samples are collected at the times selected by the clinic, allowing the laboratory to compare glucose levels as your body processes the drink.

The appointment can take several hours. You may need to remain seated and avoid food, smoking, and exercise while waiting. Nausea or light-headedness can occur; tell staff promptly so they can help you safely.

Follow the clinic’s exact instructions about fasting, medicines, water, and arrival time. Bring a snack for after the final sample if staff say this is suitable, and arrange your day so you are not rushing between collections.

The [Glucose Tolerance Test](/treatments/pregnancy-and-birth-care/glucose-tolerance-test/) page covers its purpose. Related pregnancy monitoring may be included in an [Antenatal Care Package](/treatments/pregnancy-and-birth-care/antenatal-care-package/).

Tell the team immediately about faintness, vomiting, severe weakness, confusion, breathing difficulty, or any symptom that feels alarming. Contact the clinic before attending if you are unwell, cannot fast as instructed, or need advice about a regular medicine.

How long will I be at the clinic? Which medicines can I take? May I drink water? What happens if a sample is difficult to collect or I vomit? When will the result be explained?