A Glucose Tolerance Test (GTT) is a test that measures how well the body is able to process glucose (sugar). It is usually done to diagnose gestational diabetes or to evaluate how well treatment for diabetes is working.

Pre-test preparation: You will likely be instructed to fast for 8 to 12 hours before the test. Your doctor may also advise you to avoid certain medications, such as diuretics or steroids, for a period of time before the test.

Testing method: You will be given a sugary drink, and your blood glucose levels will be measured at regular intervals over a period of 2 to 3 hours.
If testing for gestational diabetes, it is typically a 3-hour test in which a baseline blood sample is drawn, then a sugary drink is consumed, and blood samples are taken again at 1 hour, 2 hours and 3 hours.

Common symptoms that may prompt your doctor to order a GTT include: unexplained weight loss, increased thirst, and increased urination.

Diagnosis: The results of the GTT are used to diagnose diabetes or gestational diabetes.

Reference range:
Fasting glucose: 70-99 mg/dL
1 hour after glucose load: less than 140 mg/dL
2 hour after glucose load: less than 120 mg/dL
3 hour after glucose load: less than 140 mg/dL

Normal values may vary depending on the laboratory that performs the test.

Medical disclaimer: The information provided is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. It is important to follow the instructions given by your doctor or the laboratory performing the test.