What Is A Glucose Tolerance Test? Why Is It Performed? Check Details

The glucose tolerance test is a process that measures the body’s response to sugar or glucose, often used to diagnose type 2 diabetes or prediabetes and identify insulin resistance. The test can also help to find out whether diabetes is causing existing symptoms. It can also be used to identify gestational (pregnancy-related) diabetes, where blood sugar levels are often higher due to changes in the metabolism during pregnancy. However, they usually come back down after the birth.

Talking about why is it conducted, Dr Manisha Arora, Director of Internal Medicine, CK Birla Hospital, Delhi, during an interview with The Indian Express shared that blood samples are drawn every 30 to 60 minutes, up to 3 hours, to determine how quickly glucose can be cleared from the blood. “This is normally indicated in diabetes to determine insulin resistance or during pregnancy and sometimes in reactive hypoglycemia, in specialised conditions like acromegaly. It is also done in some rare carbohydrate metabolic disorders”, he said.

Following the test, GTT analyses the issues that the body might be facing while handling sugar after a meal. In simple terms, after the body breaks down food into sugar, which enters the body and is used for energy, the test reveals if the breakdown is happening too quickly.

Glucose Tolerance Test Procedure

According to the National Institutes of Health (NIH), blood is initially taken to determine one’s baseline blood sugar level. The blood is drawn from a vein, fingertip, or earlobe. After that, the patient needs to drink 75 grams of glucose to ascertain proper results. For children, the amount is based on their body weight. If the test is being done to confirm suspected diabetes, blood is drawn again after two hours and the blood sugar level is measured. On the other hand, for testing in the case of gestational diabetes, blood is drawn one hour after drinking the solution and then again after another two hours.

What Are The Interpretations Of The Test?

• In normal results, the blood sugar levels return to their usual form within 2 hours.
• In cases of impaired glucose tolerance or prediabetes, blood sugar levels are higher than usual but below the diabetic range.
• In diabetes, blood sugar levels are significantly elevated.