How Is The Oral Glucose Tolerance
Test Used To Diagnose Pre Diabetes?

The Oral Glucose Tolerance Test (OGTT) is commonly considered the gold standard for type 2 diabetes testing as well as pre diabetes testing, and involves the drinking of a sweet liquid.

Oral Glucose Tolerance Test

This test must be performed by a qualified medical professional and cannot be self-administered.

A Closer Look

This test is given after a night of fasting and involves the drinking of a sweet liquid and then regular blood draws over the next three hours.  The test measures the rate at which blood sugar levels spike and then recede after drinking the liquid.  A fast recovery indicates that the body is producing insulin properly; a slow recovery may indicate pre diabetes or possibly Type 2 diabetes depending on how high the sugar levels are.

 In addition, the OGTT is one that may be familiar to many women receiving prenatal care, as it is widely used to test for gestational diabetes.

For the Oral Glucose Tolerance Test, blood sugar results between 140-200 milligrams per deciliter (mg/dL) indicate pre diabetes, while a reading of 200 mg/dL or more indicates Type 2 diabetes.

 Exactly how much is a deciliter, you ask?  It’s one-tenth of a liter, which is approximately 3.3 fluid ounces. 

The OGTT also requires fasting prior to testing.  The minimum fasting period is eight hours but you should not fast more than 16 hours prior to taking the test.  Usually, the test is administered first thing in the morning and involves drinking 75 grams of glucose.  For the next three hours, blood is drawn and tested to measure the rise and fall of glucose in the blood. 

In people without pre diabetes or Type 2 diabetes, blood sugar levels will rise, but soon return to normal since glucose is being utilized by the body’s cells.  In someone with pre diabetes or Type 2 diabetes, glucose levels will spike and remain elevated, indicating poor utilization of glucose and resistance to insulin.

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