Curing Diabetes

A 2-hour oral glucose tolerance test determines your patient’s ability to adjust to and dispose of a glucose load. The test is especially helpful for detecting diabetes in the following patients:

• those who show signs and symptoms of diabetes but have normal fasting blood glucose levels
• those who have risk factors for diabetes but have normal fasting blood glucose levels
• those who have complications usually associated with diabetes.

After the patient fasts for 8 hours, a blood sample is obtained by venipuncture. Next, the patient drinks 75 to 100 grams of glucose. Then additional blood samples are obtained at 30 minute to 60 minute intervals for 2 hours.

The results of an oral glucose tolerance test are normal if the initial fasting blood glucose level is 70 to 115 mgjdl, the final 2-hour glucose level is less than 125 mgjdl, and all glucose values in between are less than 200 mgjdl. Despite two normal fasting blood glucose test results, a physician can diagnose diabetes in a nonpregnant adult who has an oral glucose tolerance test in which the 2-hour plasma glucose level is 200 mgjdl or more.

The 2-hour oral glucose tolerance test isn’t used to monitor a patient’s diabetes treatment. However, it can be used to monitor patients who have impaired glucose tolerance and who are at risk for developing diabetes later in life. Despite a normal fasting glucose test result, a physician can diagnose a patient with impaired glucose tolerance if the 2-hour glucose level is 140 to 200 mgjdl.

Nursing considerations

When preparing your patient for a 2-hour oral glucose tolerance test, instruct her to maintain a normal diet and activity level for 3 days before the test. Failure to do so may interfere with the test results. Some drugs such as diuretics, nicotinic acid, and betablockers may also interfere with test results. High doses of some hormones can affect the results, as well. When possible, the patient’s physician will discontinue these drugs for 3 days before the test.

The patient will need to fast for 8 hours before the test. Try to schedule it for the morning so that most of the fasting time will occur while she’s sleeping.

Instruct your patient to drink the glucose solution within 5 minutes. During the 2 hours required for the test, the patient should remain seated and not smoke.

Hypoglycemia probably won’t occur after a glucose load has been administered to a patient suspected of having diabetes, but it could occur if the patient has another unsuspected disorder, such as islet cell tumors. If the patient develops signs and symptoms of hypoglycemia, draw a blood sample for confirmation. If the patient is hypoglycemic, stop the test immediately and provide the appropriate treatment.

Send all samples to the laboratory immediately or refrigerate them to prevent altered test results.

Filed under: Diabetes Tests