Test Overview The oral glucose tolerance test (OGTT) measures the body's ability to use a type of sugar, called glucose, that is the body's main source of energy. An OGTT can be used to diagnose prediabetes diabetes gestational diabetes
Why It Is Done
An OGTT may be done to:
Check for prediabetes and diabetes. Check pregnant women for gestational diabetes. How To Prepare
Tell your doctor about all the prescription and non-prescription medicines you are taking. You may be told to stop taking certain medicines before the test. Do not eat, drink, smoke, or do strenuous exercise for at least 8 hours before your first blood sample is taken. (You can drink water before the test.) Load More Information about Oral Glucose Tolerance Test (OGTT)
How It Is Done
A blood sample is taken when you arrive for the test. This is your fasting blood glucose value. It will be compared to other glucose values in your blood. You will drink a small cup of very sweet liquid that contains 50, 75, or 100 grams of glucose. You will have more blood tests over 1 to 3 hours. Since activity can affect test results, you will be asked to sit quietly during the entire test. Do not eat during the test. You may drink water during this time. How long the test takes The test may take up to 3 hours, plus the time it takes for the doctor to meet with you.
Watch How It Feels
You may find it hard to drink the extremely sweet glucose liquid. Some people feel sick after drinking the glucose liquid and may vomit. Vomiting may prevent you from completing the test on that day.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
You may feel faint from having several blood samples taken in one day. But the amount of blood taken will not cause significant blood loss or anemia.
Risks
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Some people's blood glucose levels drop very low toward the end of the test. But some people feel like their sugar levels are low, when their levels actually are not low. Symptoms of low blood glucose include weakness, hunger, sweating, and feeling nervous or restless. If you develop these symptoms during the test, you may have your sugar level checked quickly with a glucose meter. If your level is very low, the test will be stopped.
Results
Normal Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
High values High glucose levels may be caused by:
Low values Low glucose levels may be caused by:
Certain medicines, such as medicines used to treat diabetes, some blood pressure medicines (such as propranolol), and some medicines for depression. Decreased production of the hormones cortisol and aldosterone (Addison's disease Problems with the thyroid gland or an underactive pituitary gland A tumour or other problems of the pancreas. Liver disease. Many conditions can change blood glucose levels. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.
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Current as of: April 30, 2024
