Two-hour blood sugar test

A clinician usually takes a starting blood sample, gives you a glucose drink, then collects another sample around two hours later. The change between the readings shows how quickly glucose leaves your bloodstream. Results are interpreted with your symptoms, medical history and other tests; one reading does not explain every cause of high or low glucose.

The test may help assess [Prediabetes](/conditions/prediabetes/) or [Type 2 Diabetes](/conditions/type-2-diabetes/). It is different from a [Continuous Glucose Monitor](/technology/continuous-glucose-monitor/), which tracks glucose repeatedly through a sensor.

Follow the clinic’s instructions about fasting, medicines and usual activity. Bring a list of medicines and tell the team if you are pregnant, unwell, or have recently changed your diet or treatment. During the test, remain at the clinic if asked, avoid strenuous activity, and report nausea, sweating, shakiness or faintness. Do not change diabetes medicines unless the prescribing team tells you to.

Plan a snack for afterwards if the clinic recommends one. Your clinician can explain whether you need [Diabetes Screening](/treatments/diagnostics-and-screening/diabetes-screening/) or another type of glucose test.

Tell staff immediately if you feel faint, confused, very sweaty or unwell during testing. Outside the appointment, seek urgent help for severe drowsiness, confusion, vomiting with inability to drink, or breathing that is unusually deep or fast. Arrange follow-up if results are abnormal, especially if you have increased thirst, frequent urination, blurred vision or unexplained weight change.

Ask why this test was chosen, whether you need to fast, how your medicines should be taken, and when results will be available. Ask what the next step would be if the result suggests prediabetes or diabetes, including education or medication support.