Oral Glucose Tolerance Test

The oral glucose tolerance test measures the body’s ability in glucose metabolism and clearing excess glucose in a bloodstream.

Oral glucose tolerance test

The oral glucose tolerance test (OGTT), can also be called a glucose tolerance test or a sugar tolerance test. It is used to measures the body’s ability in glucose metabolism and clearing excess glucose in the bloodstream. The test is useful in the diagnosis of diabetes, gestational diabetes, and pre-diabetes.

Importance of the OGTT

OGTT is better able to diagnose high blood glucose after a glucose challenge than the fasting blood-glucose test. The doctor may recommend OGTT, if he/she suspects diabetes in cases where patients fasting, the blood glucose level is normal, but have other symptoms of diabetes or overweight.

An OGTT is most commonly preferred to check for diabetes that happens during pregnancy (gestational diabetes).

The oral glucose tolerance test procedure

OGTT test needs at least 8 to 12 hours of fasting. In addition, another test after the patient drinks a glucose-rich beverage, typically a drink containing 75 grams of carbohydrates (other different levels of glucose consumption are also possible, but the result may be analyzed accordingly). Blood will be drawn and tested after one hour and two hours after having a glucose beverage.

What is Oral glucose tolerance?

Oral glucose tolerance means the body ability to tolerance against the consumption of a certain amount of glucose. That is how effective the body is in breaks down (metabolizes) blood glucose.
OGTT provides details about how quickly glucose is absorbed into the bloodstream for use by body cells as energy. The rate of glucose clearance depends on the amount of glucose consumed. After fasting, the normal blood-glucose rate is 60 to 100 mg/dl.

Normal, pre-diabetes, diabetes OGTT blood glucose level

For 75 grams of glucose consumption; the normal, pre-diabetes, diabetes blood-glucose levels are as below.

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Oral glucose tolerance test is useful to diagnose diabetes, as well as provides additional information about the body’s ability to metabolize blood glucose. Higher OGTT values are likely to reflect diet, lifestyle problems and problems of insulin functioning.