How the glucose tolerant test is performed?

The glucose tolerant test is performed to assess patients at increased risk of developing type 2 diabetes. About 25% of patients who have either impaired fasting glucose or impaired glucose tolerant will develop type 2 diabetes over the prolonged time with the condition. The results of this testing method cannot be utilised to differentiate between type 1 and 2 diabetes, and it cannot be used to foresee the probability of future complications or response to therapy.

OGTT examine the ability of a patient to secrete insulin in response to the oral load of glucose. The diagnosis of diabetes is made of the sequence of increasing plasma glucose levels during fasting state; the OGTT is used to illustrate the borderline in increased fasting levels of glucose. The test is not to be used on a patient who meets the standard for diabetes and is solely necessary if the fast or random glucose levels are equivocal e.g. 5.6 – 7.0 mmol/l.

About 90% of pregnant women who have diabetes have gestational diabetes that can or cannot resolve after giving birth. OGTT is useful in the diagnosis of gestational diabetes in pregnant women. Its recommended by NICE (National Institution for Health Care Excellence) that midwives, doctors and other healthcare professionals should diagnose pregnant women with gestational diabetes if they have fasting plasma [glucose] of 5.6 mmol/l or higher or a 2hrs plasma [glucose] of 7.8 mmol/l or higher. However, 75g 2hr OGTT is not recommended to be routinely offered for women diagnosed with gestational diabetes and those who have blood glucose levels to normal after giving birth.