7800 Wolf Trail Cove, Germantown, TN 38138 • (901) 682-9222 • Open Weekdays 8:00 - 5:00
ORAL GLUCOSE TOLERANCE TEST
An oral glucose tolerance test (OGTT) measures the body's ability to use glucose. Glucose is a type of sugar found in fruits and many other foods and is the main source of energy for the body. An oral glucose tolerance test is performed to detect problems in the body's metabolism of glucose. This test is most commonly used to diagnose gestational diabetes between 24 and 28 weeks of pregnancy and is crucial in protecting the health of the fetus. The one-hour test is used for diabetic screening and the three-hour test is used if the one-hour test is abnormal. This test can also be used to diagnose diabetes.
The pancreas releases insulin into the bloodstream to regulate the body's processing of glucose. By measuring the amount of glucose in the blood after a concentrated amount of glucose is ingested, it is possible to assess how well insulin is functioning.
The OGTT is performed in a lab or a doctor's office by a lab technician or nurse. In most cases the test is completed within one to 3 hours, some cases may require up to 6 hours to complete. Test results are usually available within 1 day.
Preparation for the test includes:
- Eat and exercise normally for three days prior to the test. Be sure to consume sufficient carbohydrates.
- Discontinue medication three days before testing
- Ingest nothing but water for ten hours before the test (only applies to the 3-hour test).
- Avoid smoking before the test.
Test Procedure
After not eating all night, the person being tested drinks a special sugar solution on the morning of the test. A blood sugar sample is taken from a vein in the person's arm once each hour for 3 hours to see how much the blood sugar increases and then decreases over time. Children may be required to perform a urine test also. For the one-hour test it is not necessary to fast the night prior to the test.
You may experience mild discomfort when the needle is inserted. Also, the glucose solution can be unpalatably sweet.
Normal activities and medication may be resumed immediately after the test. Some people may develop low blood sugar three to five hours after the test. Eating a small meal upon completion of the test should correct blood sugar levels.
Interpretation
Above normal levels of glucose may indicate diabetes or gestational diabetes. If diabetes is indicated treatment may begin immediately. If gestational diabetes is diagnosed, the condition may be controlled with increased exercise and diet modifications.
If the diagnosis is impaired glucose tolerance the patient will be monitored for the development of diabetes. People with this condition are advised to modify their diet or increase physical activity to decrease your risk of developing diabetes or heart disease.
Failure to maintain normal exercise and diet routine before the test, illness, anxiety or smoking or consuming caffeine before or during the test can adversely affect results.
Thomas G. Stovall, M.D.
Dr. Stovall is a Clinical Professor of Obstetrics and Gynecology at the University of Tennessee Health Science Center in Memphis, Tennessee and Partner of Women's Health Specialists, Inc.
Date Published: 2004-03-10
7800 Wolf Trail Cove, Germantown, TN 38138
Phone: (901) 682-9222; Fax: (901) 682-9505