A glucose tolerance test for diabetes is more effective when diagnosing gestational diabetes. The test can be effective in the diagnosis of type two diabetes, but may need to be administered several times. Some individuals who test outside of normal ranges may not develop diabetes if they modify their diet and physical fitness habits. In terms of long-term accuracy, the glucose tolerance test for diabetes is good at predicting the eventual development of the disease.
The purpose of a glucose tolerance test for diabetes is to measure how an individual's system responds to a high level of sugar. If the pancreas is unable to produce enough insulin to control the amount of blood sugar that circulates at one time, these levels can become higher than 140 milligrams per deciliter (mg/dl). Anything between 140 and 199 mg/dl indicates a glucose intolerance, which is considered to be a pre-diabetic condition. When a glucose tolerance test for diabetes yields results of 200 mg/dl or over, it can indicate that the individual has fully developed the disease.
In order to be as effective as possible, a glucose tolerance test for diabetes must be administered under certain conditions. The patient should fast for at least eight hours prior to the taking the test. Anyone who undergoes glucose tolerance testing needs to be aware that the results can be affected by other underlying diseases or conditions. Some doctors recommend consuming a high carbohydrate diet at least three days prior to taking the test.
When the test results indicate that a patient could have type two diabetes, a second or third test may be administered in order to confirm the diagnosis. This is because there are so many circumstances that might skew the test results, including physical activity level, mild illness, inability to fast properly, and timing. Some individual test results might indicate borderline blood glucose levels, which may need to be re-checked and evaluated for accuracy.
Glucose tolerance tests are not necessarily given to diagnose a case of type two diabetes. They tend to be used to determine whether a female has developed diabetes as the result of her pregnancy. The test is usually given to someone who has a good health history, is relatively physically active, and is not on any prescription medications that might skew the results. Drinking coffee and smoking cigarettes on the day of the test can also dramatically alter the test's accuracy.