A glucose challenge test, also known as the oral glucose tolerance test, is used to measure the body's ability do utilize glucose. The monitoring of glucose, the main source of energy for the body, is important because an excess of it in the blood stream is an indication of diabetes. The oral glucose challenge test is therefore used to diagnose diabetes or the risk of developing it. Usually for taking the glucose challenge test, pregnancy is the right time since the test is mostly used to check for pregnancy related diabetes.
The test is usually done to check for gestational diabetes in pregnant women. If a woman had developed gestational diabetes in a previous pregnancy, the test is conducted for every subsequent pregnancy. Women who are overweight at the time of getting pregnant are also recommended to have this test conducted. Women with polycystic ovarian syndrome should also get this test done because the chances of developing diabetes are quite high in this case.
No elaborate preparations are needed for the test. However, it is recommended that nothing should be eaten about eight hours prior to the test. Just before the test, you will have to drink a glucose solution quickly. About one hour later, your blood is taken for the test. The one hour gap is taken because the glucose levels peak one hour after consumption of glucose and then begin to drop subsequently. This is only the first part. If the glucose challenge test results show that you have gestational diabetes, further diagnosis is done. Read more on GTT test
The glucose liquid is usually extremely sweet and you may begin to feel sick after drinking it. A lot of people have been known to vomit just after they have consumed the liquid. However, if you do vomit, you will have to take the test again on another day.
Though normal values differ, the usual normal range when 50 grams of glucose is taken and the screening test is done one hour later is lower than 140 mg/dL or 7.8 mmol/L; anything greater than that requires a further diagnostic test.
There are several reasons why the values may be higher than normal. Apart from gestational diabetes, polycystic ovarian syndrome and corticosteroids based medications can also interfere with the test results. People under sever stress or those suffering from Cushing's syndrome and other inherited diseases like cystic fibrosis, may also show abnormal test results.