Oral glucose tolerance test

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

What is Oral glucose tolerance test OGTT

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

Importance of OGTT
OGTT is better able to diagnose high blood glucose after a glucose challenge than the fasting blood glucose test. Doctor may recommend OGTT, if suspects diabetes in cases where a patient’s fasting 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).

Oral glucose tolerance test procedure
OGTT test is carried out after at least 8 to 12 hours of fasting. And another test after the patient drink a glucose-rich beverage, typically a drink containing 75 grams of carbohydrates (other different level of glucose consuption is also possible, but the result may be analyzed accordingly). Blood will be drawn and tested after one hour and two hours after having glucose beverage.

What is Oral glucose tolerance
Oral glucose tolerance means the body ability to tolerance against the consumption of 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 metabolized from 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.

Normal:           139 mg/dl or 7.72 mmol/l and below
Pre-diabetes: 140 to 199 mg/dl or 7.77 to 11 mmol/l
Diabetes:        200 mg/dl or 11.1 mmol/l and above

Oral glucose tolerance test is used not only to diagnose diabetes, but also help to provide 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.