What should you know about an OGTT laboratory test?

An OGTT laboratory test measures how your blood glucose changes after you drink a measured glucose solution, often during pregnancy. OGTT stands for oral glucose tolerance test. The test gives a time-based picture of glucose handling rather than relying on one blood sample alone. It may be called a glucose tolerance test or a sugar test in pregnancy.

A clinician may recommend an OGTT when pregnancy care needs a closer check of blood glucose, or when another result suggests that glucose regulation should be assessed. A baseline blood sample is usually taken first. You then drink the glucose solution, followed by further blood samples at times chosen by the laboratory or maternity team. The results are interpreted against the laboratory's pregnancy-specific or non-pregnancy reference range.

A result outside the reference range does not by itself explain every aspect of your health. Your clinician considers the timing of each sample, your pregnancy stage, medicines, symptoms and other test results before discussing what the finding means.

Follow the laboratory's instructions about fasting, eating, drinking water, medicines and activity. Do not change prescribed treatment unless your maternity or medical team tells you to. Plan to remain at the testing site while samples are collected, because eating, strenuous activity or leaving early can affect the interpretation. Wear comfortable clothing, bring a snack for afterward if advised, and tell staff if you feel unwell, feel faint or vomit after drinking the solution.

The glucose drink can taste very sweet. Rest quietly between samples and ask whether plain water is allowed. If you cannot complete the drink or the collection schedule, tell the team so they can record it and explain the next step.

Tell the testing staff promptly if you develop marked dizziness, sweating, shaking, weakness, nausea or vomiting during the test. They may pause the procedure and decide whether you need immediate assessment. After leaving, contact your care team if you remain faint, cannot keep fluids down, or feel increasingly unwell. During pregnancy, seek urgent maternity advice for severe symptoms or any concern that feels sudden or serious, rather than waiting for the result.

Ask which preparation instructions apply to you, whether your regular medicines should be taken, how long the visit may take, and when and how the result will be explained. If fasting is difficult because of nausea, diabetes treatment or another condition, mention this before the appointment so the team can plan safely.