A physician orders a glucose test when he or she is trying to diagnose diabetes. There are two main types of glucose tests:

  • Fasting plasma glucose test (FPG): For this test to be effective, you must fast from, or refrain from, all food or drink except water for eight hours before the test. A technician draws your blood into vials. Then at the laboratory, your plasma — the fluid part of your blood — is used to determine the level of glucose in your plasma.
  • Oral glucose tolerance test (OGTT): This test evaluates how well your body handles a set amount of glucose. A lab technician draws your first blood sample and then gives you a premeasured glucose beverage to drink. After two hours, your blood is drawn again to determine how well your blood has processed the sugar. Your physician will then compare the two blood samples.

The results of these tests, in addition to other symptoms you may be experiencing, will help your physician determine a diagnosis of prediabetes or type 2 diabetes. Either diagnosis can greatly increase your risk of heart disease and stroke. Diabetics are two to four times more likely to develop cardiovascular disease from a number of risk factors, including:

  • High blood pressure
  • Lipid disorders
  • High LDL (bad) or low HDL (good) cholesterol
  • High triglycerides
  • Smoking
  • Obesity
  • Inactivity
  • Poorly controlled blood sugars

Once you have been diagnosed with diabetes, everyday glucose monitoring is necessary for proper diabetes management and to minimize dangerous complications like heart disease or stroke. Everyday monitoring can be done at home with personal blood glucose monitors.

What to expect during a glucose test

Preparing for your procedure

Always check with your physician for special instructions when scheduling your glucose test. It is important for you to eat and drink normally in the days leading up to the test.

Do not eat or drink anything for at least eight hours prior to your fasting plasma glucose test. No fasting is necessary for the oral glucose tolerance test; however, you will need to schedule the test when you have two hours available for the entire test. Check with your physician to determine if any of your medications should be avoided for the days leading up to your scheduled test. Make sure to bring all of your medications, as well as any herbal or dietary supplements and over-the-counter medications, to the test with you.

During your procedure

During the fasting plasma glucose test, make sure to hold still while the technician is drawing your blood. During the oral glucose tolerance test, it is very important that you avoid eating, drinking or smoking during the two-hour period between blood tests. You can bring a book or magazine to read while you wait.

After your procedure

You can resume normal daily activities once the test is over. You might want to bring a small snack to eat after the oral glucose tolerance test to help flush the sugary drink out of your system. Your physician will contact you with the test results to determine the appropriate next steps.

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