How to Perform Glucose Tolerance Tests

The glucose tolerance test is used to diagnose diabetes. It is used to determine the presence of type 2 diabetes as well as gestational diabetes in pregnant women. When conducting a glucose tolerance test, it is helpful to be understanding of patients who must spend several hours in a clinic or lab until the testing process is complete. If you are performing the glucose tolerance test, you will need to be a certified phlebotomist, nurse or other health care professional trained to legally draw blood.

Instructions

• 1

  Give the patient who is having the glucose tolerance test his instructions the day prior to the appointment. Inform the person that the glucose tolerance test is a fasting test. Tell the patient to refrain from eating or drinking anything after midnight or for 8 to 12 hours before the appointment.

• 2

  Confirm that the patient has successfully fasted at the time of the appointment, prior to drawing blood. Reschedule the glucose tolerance test if the patient failed to fast.

• 3

  Draw a vial of blood at the time of the appointment. This is considered the baseline or fasting glucose level.

• 4

  Ask the patient to wait while the blood sample is sent to the lab. If the lab results show that the serum glucose is less than 130 mg, you can proceed with the test. If higher than 130 mg, contact the patient's physician before proceeding.

• 5

  Give adult, non-pregnant patients a sweetened drink that contains 75 grams of glucose. Pregnant women are given a drink that contains 100 grams glucose. The amount of the glucose drink that is given to children will depend on the age of the child.

• 6

  Draw a blood sample every 30 to 60 minutes or five times over a 3-hour period, or intervals as instructed by the ordering physician. Occasionally when diagnosing type 2 diabetes versus gestational diabetes, the ordering doctor will request that the patient sit quietly for 2 hours after ingesting the glucose drink, before the blood is drawn.