Definition – What is a glucose tolerance test?
The oral glucose tolerance test (oGTT) is a test that checks the body’s glucose processing. Elevated blood sugar levels in this test indicate a glucose tolerance disorder or even diabetes mellitus. The oral glucose tolerance test is performed as part of prenatal care between the 24th and 28th week of pregnancy to rule out gestational diabetes.
Indications
The glucose tolerance test is performed in all pregnant women between the 24th and 28th week of pregnancy as part of prenatal care. In case of risk factors for gestational diabetes, such as gestational diabetes in a previous pregnancy, the fasting blood glucose can be determined before the 24th week of pregnancy.
Preparation – Do you have to be sober?
In the glucose tolerance test, two forms must be distinguished. The “normal” glucose tolerance test (75g-oGTT) and the pregnancy glucose tolerance test (50g-oGTT) differ in the amount of sugar in the drinking solution. The pregnant woman does not need to be fasting for the pregnancy test. However, if this test shows elevated values, the regular 75g-oGTT must be repeated. For this test you should be fasting in any case, i.e. you should not have eaten anything or drunk any sweet drinks 12 hours before the test.
Procedure
In the glucose tolerance test during pregnancy, the patient must drink a sugar solution containing 50g of glucose. After one hour waiting time the blood sugar value is measured now. If it is below 135mg/dl, pregnancy diabetes can be ruled out.
If the value is above 135mg/dl, the blood sugar is considered elevated. The 75g-oGTT should then be performed again on another day. In this case the patient must be fasting and a fasting blood sugar level must be determined. A sugar solution with 75g glucose is then drunk. After 2 hours a new blood sample is taken to determine the blood sugar.
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