Blood Glucose Tolerance Test in Pregnancy

Blood is taken before and after the drink so the care team can compare glucose levels over time. Follow the clinic's preparation instructions because food, drink, illness, and some medicines can affect the test.

The first sample measures glucose after the requested fasting period. You then drink a measured glucose solution and remain at the clinic until later samples are collected. The test shows whether glucose stays higher than the pregnancy care team expects after your body has had time to process the drink.

An abnormal result can support a diagnosis of gestational diabetes; it does not mean you caused the condition. Pregnancy hormones can reduce insulin's effect, allowing glucose to remain in the bloodstream. Your maternity team interprets the samples using its laboratory thresholds.

Check when fasting should begin and whether plain water is allowed. Ask specifically how to handle prescribed medicines; do not stop them without instructions. Bring something quiet to do, as you will need to stay seated and avoid eating, smoking, or physical activity while samples are pending.

Tell staff before the test if you are vomiting, acutely unwell, unable to fast safely, or have had surgery that changes digestion. If you vomit the glucose drink, alert the team rather than trying to continue unnoticed; they will explain whether another approach or appointment is needed.

During the appointment, immediately report faintness, sweating, shaking, confusion, breathing difficulty, or feeling unable to continue. Staff can assess you and stop the test if necessary. Mild nausea can occur after the sweet drink, but worsening symptoms still deserve attention.

Outside the test, seek urgent maternity advice for severe illness, persistent vomiting with difficulty keeping fluids down, reduced baby movement once movements are established, or any other pregnancy warning sign your care team has discussed.

Confirm the fasting instructions, permitted medicines, planned blood-sample times, and when results will arrive. If glucose is raised, ask who will help with food choices and glucose monitoring, whether medicine may be considered, and how follow-up will fit into antenatal care.