Glucose Tolerance Test

Around 24-28 weeks of pregnancy your doctor will likely want to screen you for gestational diabetes. Gestational diabetes is a form of diabetes that may develop during pregnancy. Gestational diabetes is distinguished from other types of diabetes because it occurs during pregnancy, it was not diagnosed prior to pregnancy, and it usually, but not always, disappears following delivery.

One hour Glucose Tolerance Test

For the one hour glucose tolerance test no fasting is required. When you arrive to the office, you will receive 50 gm of a high glucose solution. You will usually be offered several different flavor options, such as, lemon/lime, cola, and orange. You should consume the entire beverage within 5 minutes. You should be aware that the glucose solution is very sweet and many women will feel nauseous after drinking it. The nurse will record the time the glucose beverage was given and return in one hour to draw a blood sample. If you should feel symptoms of hypoglycemia, such as dizziness, weakness, sweating, or hunger at any time during the test please inform the nurse.

Results of the one hour glucose tolerance test

If your blood glucose level exceeds 130 mg/dl, a three hour glucose tolerance test will be necessary. (Ladewig, London, Moberly, Olds, 2002)

Three hour Glucose Tolerance Test

The three hour glucose tolerance test is is similar to the one hour test with a few distinctions. You should be instructed to maintain a high carbohydrate diet for three days prior to testing. This should be followed by fasting for 10-16 hours. It will be easiest for the pregnant women to eat her dinner meal before 7 pm and fast until morning. Plan to arrive at the doctor's office or lab between 7:00 a.m. - 9:00 a.m. to avoid prolonged fasting. When you arrive for the test, the nurse will draw your blood and collect a urine sample. She will then give you a 100 gm glucose solution. She will record the time and return to collect blood and urine samples at 30 minutes, 1 hour, 2 hours, and 3 hours for a total of 5 blood and urine samples. You will not be able to eat or drink anything except for water throughout the duration of the test. You should be encouraged to drink water, however, because frequent urine samples will be needed.

Results of three hour glucose tolerance test

Gestational diabetes will be diagnosed if two of the following values are exceed the normal limit.

Fasting - 95 mg/dL 1 hour - 180 mg/dL 2 hours - 155 mg/dL 3 hours - 140 mg/dL

Gestational diabetes can cause health risks for mother and baby. It is important to follow up with your health care provider to establish a plan of care to manage diabetes.

References

Ladewig, P., London, M., Moberly, S., Olds, S. (2002). Contemporary Maternal-Newborn Nursing Care. Upper Saddler River, NJ: Prentice Hall

LeFever Kee, J. (2001). Handbook of Laboratory and Diagnostic Tests. Upper Saddler River, NJ: Prentice Hall

Mc Cann, et al. (2002). Diagnostic Tests Made Incredibly Easy. Springhouse, PA: Springhouse

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