The amount of sugar in the blood can be measured and the results used to determine whether a person has diabetes. The two most common tests are Fasting Blood Glucose (FBG) and Random Blood Glucose (RBG). FBG testing is done at the end of an 8-hour period without food, and is currently the preferred diagnostic test. The Glucose Tolerance Test (GTT) is considered less reliable and has fallen into disfavor except in cases of pregnancy or as an additional test to confirm borderline cases. GTT is measured 2 hours after a dose of 75 grams of glucose has been administered.