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Doctors can learn about fasting glucose levels from the glucose challenge test. For example, a doctor may order a glucose challenge test to help in diagnosing glucose intolerance, which is the impaired ability to metabolize, or break down and use, sugar. The test is also useful for diagnosing gestational diabetes, which is a type of diabetes that sometimes develops during pregnancy and usually disappears after the pregnancy is over. The test requires a patient to fast, usually overnight, and then consume glucose in liquid form. After this, the patient must wait — without eating or drinking anything — for a specific amount of time and then have his blood drawn to test his blood glucose levels.
A glucose challenge test is used to determine how well the body is metabolizing sugar and to identify patients who may have glucose intolerance. This can prove an important test when a doctor suspects that a patient has diabetes or gestational diabetes. The test is more often used in testing for gestational diabetes, however.
When a doctor orders a glucose challenge test, the patient is usually required to fast for about eight hours, typically overnight, before having the test performed. After fasting, he is usually given a sugary solution to drink that contains a specific amount of glucose. Often, the flavor is similar to that of a flat soda. Then, the patient is required to wait a period of time and have his blood drawn. It is this blood test that gives the doctor insight into how well the patient's body is processing sugar.
It is important to note that an abnormal test result doesn't necessarily mean the patient has diabetes or gestational diabetes. In some cases, abnormal results may simply mean that the patient's ability to metabolize sugar is impaired, and he may be at risk for developing one of these conditions. A doctor may also use other methods to make a definite diagnosis. For example, a doctor may also test the level of insulin, which is a substance that is critical in the processing of sugar in the body.
In some cases, the glucose challenge test involves the use of more than one blood test. For instance, a patient may be given a blood test after fasting for eight hours but before drinking the glucose solution. Then, he will usually have to drink the solution and wait for a period of time before having another blood test. In making a diagnosis, doctors usually compare fasting blood sugar levels to the patient's levels after drinking the solution.