The blood glucose test is ordered to measure the amount of glucose in the blood right at the time of sample collection. It is used to detect both hyperglycemia and hypoglycemia and to help diagnose diabetes. Blood glucose may be measured on a fasting basis (collected after an 8 to 10 hour fast), randomly (anytime), post prandial (after a meal), and/or as part of an oral glucose tolerance test (OGTT / GTT). An OGTT is a series of blood glucose tests. A fasting glucose is collected; then the patient drinks a standard amount of a glucose solution to "challenge" their system. This is followed by one or more additional glucose tests performed at specific intervals to track glucose levels over time. The OGTT may be ordered to help diagnose diabetes and as a follow-up test to an elevated blood glucose.