What Is An Oral Glucose Tolerance Test (OGTT) And When Is It Done?

— -- Question: What is an oral glucose tolerance test (OGTT) and when is it done?

Answer:Now an oral glucose tolerance test is a diagnostic test for diabetes. If the fasting blood glucose level is normal or in the impaired fasting glucose range, one may want to do an oral glucose tolerance test. This involves drinking a cola-like solution that has glucose levels and then measuring the blood glucose two hours later to find the peak response to this ingestion of a glucose load.

It is slightly more sensitive than the fasting glucose tolerance test. So if someone, for example, has an impaired fasting glucose -- not high enough to be diagnostic of diabetes -- they may want to have an oral glucose tolerance test with a sample taken two hours after the ingestion of the glucose load to see if it is greater than 200, which is the cutoff for having diabetes.

It is not necessary for somebody who already has diabetes to have an oral glucose tolerance test. Now the oral glucose tolerance test occasionally, because it is a sugary solution, can make people feel a little bit queasy in the stomach, a little bit nauseated, but this is really very rare. It usually (does) not make people sick to have an oral glucose tolerance test.

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