Oral Glucose Tolerance Test (OGTT) is conducted to measure the glucose level in blood in an individual. This test can be conducted to detect pre-diabetes too. Oral Glucose Tolerance Test (OGTT) is more reliable than the FPG test when it comes to diagnosing pre-diabetes. But it is not as convenient as the latter one.
In Oral Glucose Tolerance Test (OGTT), an individual is required to be in empty stomach for at least 8 hours before the test. The glucose level in blood will be noted down before Oral Glucose Tolerance Test (OGTT) is conducted. Then that person will have to drink a glass of water containing dissolved glucose of about 75 grams. After two hours, again the glucose level in blood will be noted down.
The theory behind Oral Glucose Tolerance Test (OGTT) is simple. When an individual drinks that liquid the glucose level will obviously rise in blood. If that person is free from diabetes, then the risen glucose level will fall rapidly because of the normal insulin production in his body. On the other hand, if that person has type-1 diabetes, then the risen glucose level will not fall because of the insufficient amount of insulin in his body. Below, by looking at the table, you will understand both the categorized results and their meanings.
| 2-Hour Plasma Glucose Result (mg/dL) | Diagnosis Meaning |
| 139 or <139 | Normal |
| 140 – 199 | Pre-diabetes (impaired glucose tolerance) |
| 200 or 200+ | Diabetes |
If an individual is diagnosed with Impaired Glucose Tolerance (IGT) that person should have to be very careful. It is because that person is more prone to develop type-2 diabetes later. An individual cannot be said to have diabetes with one-time conducted Oral Glucose Tolerance Test (OGTT). It is necessary to conduct another Oral Glucose Tolerance Test (OGTT) on another day to confirm the presence of diabetes in that person.
