Glucose Tolerance Test
What is the glucose tolerance test?
The oral glucose tolerance test is used to measure the body's ability to metabolize glucose. Glucose is a sugar and is the body's primary source of energy. Glucose imbalances can lead to low blood sugar or high blood sugar, commonly known as diabetes. The oral glucose tolerance test will inform your health care provider if you are experiencing complications due to a glucose imbalance. Gestational diabetes occurs in some pregnant women and the glucose tolerance test should determine if you have developed this temporary condition.
In the glucose challenge screening, you will drink a weak liquid which contains glucose (a sugar). A blood sample is then collected, typically one hour later. If this test indicates a potential problem with gestational diabetes, more tests may be ordered.
Factors that may increase your chance for gestational diabetes:
- If you experienced gestational diabetes during a prior pregnancy.
- In previous pregnancies, if you had a child that weighted more than 8.8 pounds.
- If you were overweight before your pregnancy.
When is the test done?
The glucose tolerance test is typically performed between the 24th and 28th week of your pregnancy.
How do I prepare for the test?
Eat a balanced diet for at least 3-4 days before taking the test. You should avoid poor food choices such as cake, ice cream and potato chips. You should avoid any smoking, drinking or exercise eight hours before the test is administered. Be sure to inform your health care professional of any prescription and non-prescription drugs you are taking. Some drugs can affect the test results.
How long does the complete glucose test take?
It usually takes four hours. You can not eat and will only be allowed to drink water during this testing period, because the glucose tolerance test is measuring the change in your glucose levels over the four-hour period. Food intake or beverages other than water can artificially affect glucose levels and disrupt test results. It is also best to maintain low physical activity level during the four-hour testing period. The doctors typically draw your blood at arrival to determine a good baseline glucose level. Then, the glucose liquid is ingested and blood is periodically withdrawn (typically hourly) to measure your glucose levels.
