What is a Glucose Tolerance Test?

Glucose Tolerance Test

Today, we’re going to go over the basics of glucose tolerance testing. Essentially, doctors sometimes need to measure and gauge how quickly glucose is used and removed from the blood to test for things like diabetes and other things like this (insulin resistance).

Purpose and Procedure

It’s used to analyze biological and chemical reaction to glucose for health purposes. In a basic glucose tolerance test, you begin with a 10 to 12 hour period of fasting. Prior to this time of fasting, glucose and carbohydrates and things like this, there should be a normal level of consumption that shouldn’t be restricted in any shape or form.

Normal consumption, then 10 to 12 hours of fasting. Water is permitted, but no other form of sugars or carbohydrates or food, so that the doctor can then get a baseline. The doctor who is testing will draw blood at the end of that 10-12 hours of fasting to get the baseline reading of blood glucose levels.

After they have their baseline, then they will administer, either orally or intravenously, a particular dosage of glucose. That’s been set by the World Health Organization.

They give a pre-set amount of glucose, either orally or intravenously, (orally is the primary method, but intravenous when necessary), then at specific intervals after that administration (1, 2, and 3 hours), they measure the glucose in the blood and compare it next to standardized charts to see whether or not they fall in the normal range.

We just want to go over those ranges briefly, then. Blood draws then at the baseline. The normal blood glucose level at baseline, after the fasting, would be less than 110 milligrams per decilitre. 1-2 hours after the administration of the glucose, it should be less than 200 milligrams per decilitre, then three hours it should be below 140 milligrams per decilitre.

Fasting, 110, less than 110. 1-2 hours after administration, less than two hundred. Three hours later, below 140 milligrams per decilitre. Those are the normal ranges for the body to be able to process the glucose and how much there would be then (density within the blood).

Essentially it’s a biological and chemical reaction to glucose in the blood that they’re analyzing for. Usually testing for diabetes and things like this there’s a fasting period, baseline blood draw, the administration of the glucose orally or intravenously, and then thereafter at one, two, and three hours, that’s generally when it’s done.

A blood draw is taken and the glucose level is measured. Here are the norms, again, for where it should fall if the person is in the normal range. The basic glucose tolerance test is described on the board here. We’ve gone over it briefly.


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by Mometrix Test Preparation | This Page Last Updated: January 29, 2024