Oral Glucose Tolerance Tests

One way that a doctor can diagnose type 2 diabetes is with the oral glucose tolerance test. This painless and fast test can identify how well your body is managing insulin and blood glucose levels. 

The Glucose Tolerance Test

The test begins with abstaining from food and drink for eight hours prior to testing. Three days before the test, you should focus on eating a diet rich in carbohydrates. You should also never drink coffee or smoke the morning of the test either. At the doctor’s office, you’ll drink about 75 to 100 grams of a glucose-rich drink. Then, for the next three hours, multiple samples (usually four) of blood will be drawn to test the progression of the your glucose levels.

Normal patients will experience a dramatic rise in blood glucose immediately after drinking the solution. Those with diabetes will experience the same dramatic rise (usually higher than those without diabetes), but their glucose levels will remain high while a non-diabetic’s will fall rapidly as insulin acts on the glucose in their blood.

Glucose Tolerance Tests and Diabetes Diagnosis

When you are faced with an abnormally high oral glucose tolerance test result, you are said to have “impaired glucose tolerance.” The diagnosis of diabetes comes after two different tests on two different days show an impaired glucose reaction and poor insulin response. If a patient is pregnant and undergoing this test, she may be diagnosed with gestational diabetes if her fasting plasma glucose level is high and the levels fail to return to normal after the oral glucose tolerance test. 

When a person’s glucose levels do not fall after the initial rise of glucose in their blood, a doctor will often recommend that person return for a second test on another day. It’s very important to follow up on any abnormally high result—especially if you’re experiencing diabetic symptoms or are at high risk for the condition. It is essential to diagnose diabetes and begin treatment as early as possible: unmanaged diabetes will lead to organ failure, long-term health ailments, and even death. 

Remember that being diagnosed with impaired glucose tolerance doesn’t mean you’ll automatically develop diabetes. About five percent of patients with impaired glucose tolerance will develop diabetes. Many of those diagnosed early with impaired glucose tolerance are able to avoid diabetes with changes to their lifestyle. For example, losing five to 10 percent of your body weight and engaging in just 30 minutes of moderate exercise a day, five days a week can reduce your chances of developing diabetes by nearly 50 percent!

The earlier you’re tested for impaired glucose tolerance, the earlier you can make changes that will improve your quality of life, and even potentially save you from serious long-term health issues. These changes will also save you money in the long run in terms of health costs and lost time at work.