Glucose Tolerance Test
One of the primary tools used to diagnose diabetes is the oral glucose tolerance test OGTT. In a few cases, an intravenous test may be used, but this is extremely rare. The test requires that the patient fast for eight to ten hours and then drink a large quantity of glucose. Some individuals may experience nausea as a result of the glucose consumption. A blood sample is then taken after thirty minutes, then every thirty or sixty minutes for three hours. The test measures how well the body deals with the spike in blood sugar caused by the sudden consumption of glucose.
This test is most often used to diagnose gestational diabetes. Individuals with diabetes or prediabetes will show a higher spike in glucose and a slower return to normal glucose levels. In some cases, insulin levels may also be directly tested from the same sample. The test is performed between week 24 and week 28 of the pregnancy. It can also sometimes detect the presence of polycystic ovary syndrome. Doctors recommend the test for all pregnant women who have a history of gestational diabetes, have previously given birth to a child with a birth weight of over nine pounds, or who were overweight prior to the pregnancy.
For type 2 diabetes, the oral glucose tolerance test OGTT is used when fasting glucose levels are normal, but medical professionals have other reasons to suspect the presence of the disease. The test may also reveal the presence of impaired glucose tolerance, which may or may not develop into diabetes. Doctors recommend that individuals who show signs of impaired glucose tolerance increase their activity levels and lose weight. In some cases, Metformin, normally given to type 2 diabetics, may be prescribed as a preventative measure. The diabetes association recommends that the following people should be tested for either impaired glucose tolerance or impaired fasting glucose (using the more standard fasting glucose test): individuals over 45 who are overweight and individuals under 45 who are overweight and have a family history of diabetes, a history of gestational diabetes or who have given birth to a baby of over nine pounds, or who are in a high-risk ethnic group. Symptoms which may cause a doctor to order a glucose tolerance test even if fasting glucose appears normal include excessive thirst, overactive bladder, blurred vision and fatigue.
As the test may detect elevated blood sugar before the development of full-blown diabetes, it is a valuable tool, especially to test pregnant women. Simple lifestyle changes can often prevent Type 2 diabetes from developing once a person is known to be at risk. Therefore, pregnant women and individuals who may be experiencing symptoms of diabetes should talk to their doctor about an oral glucose tolerance test OGTT.
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