The standard oral glucose tolerance test (OGTT) lasts about two hours. You should speak with your primary care physician
regarding the exact details of your specific testing.
In an OGTT you are given glucose orally and then your blood glucose level is checked two hours later. A normal value would be a glucose level less than 140mg/dL. The term impaired glucose tolerance is given if the two hour level is between 140 and 200 mg/dL. If the level is above 200mg/dL and you have symptoms of diabetes, then you are diagnosed with Diabetes Mellitus (DM).
Often, impaired glucose tolerance is a stepping point to true diabetes. It is affected by insulin resistance and obesity, which in itself causes increased insulin resistance (meaning you need more insulin to have the same effect on blood glucose). Insulin is a hormone that is made and secreted by pancreatic beta cells and is essential in the metabolism of glucose. Without it, glucose cannot be used and builds up in the blood, leading to high blood sugar levels. Having a sedentary lifestyle with minimal exercise and an unbalanced diet also can hasten the progression to diabetes.
The actual blood test is a routine blood glucose level which should return in a few hours. However, depending on your laboratory and whether testing needs to be sent out, it might take 1-2 days. After your receive the result, you should speak with your endocrinologist to discuss the results and further management or testing.