Glucose Tolerance Testing
A glucose tolerance test shows how your body handles sugar (glucose) over time. Your provider may order this test to check for conditions like diabetes or problems with blood sugar control.
If you are scheduled for glucose tolerance testing, please review the information below so you know how to prepare and what to expect on the day of your test.
What should my diet be before the fast?
You should eat a regular diet for three days before your overnight fast. Do not start a special or very low-calorie diet unless your provider tells you to.
The night before your test, follow the fasting instructions given by your provider. This usually means no food and no drinks other than water during the fasting period.
How does glucose tolerance testing work?
During the test:
- A fasting blood sample is drawn first to measure your baseline blood sugar level.
- You will then drink a solution that contains a measured amount of glucose (sugar).
- After you drink the solution, additional blood samples are drawn at set times, usually every 60 minutes, to see how your body processes the glucose.
It is important to stay at the lab until the testing is complete and to follow staff instructions between blood draws.
What if I feel sick during the test?
Some people may feel nauseated or uncomfortable after drinking the glucose solution. If you start to feel sick or think you might vomit, tell the lab staff right away.
If you vomit or cannot complete the test, the testing may need to be repeated on another day. If you have questions about what to do, your doctor is the best source of information.
If You Have Questions
If you have questions about how to prepare for your glucose tolerance test or what will happen during the test, please contact your provider before your appointment.
