Glucose is the food that the body's cells depend upon to live and reproduce. So many body systems depend on a steady, moderate supply of glucose that when the glucose level varies too much, permanent damage can occur. Low levels of glucose are called hypoglycemia and high levels are called hyperglycemia. A blood glucose test is often used to check the body's regulation of these levels.
Identification
Fasting blood glucose, or FBG, is the term used to describe the level of glucose in blood after a patient has gone for eight or more hours without eating. FBG gives doctors a picture of how well glucose is being regulated in the body. It is measured in milligrams per deciliter or one-tenth of a liter of blood plasma. Blood glucose may also be expressed using the universal scientific notation of millimoles per liter of blood plasma. A mole is a measure of atoms of a substance and a millimole is one-thousandth of a mole.
Managing Glucose
Most foods contain sugars and starches, both of which convert into glucose as they travel through the digestive system. The pancreas generates a hormone called insulin, which controls the level of glucose released into the bloodstream so that body cells are neither starved nor overdosed with the food. The pancreas is part of the endocrine system, which produces hormones to regulate body functions. Glucagon, another hormone secreted by the pancreas, draws stored glucose out of fat cells to raise glucose levels between meals or as the patient sleeps.
Comparing Readings
The fasting blood glucose test requires a fast that is long enough to empty the digestive system to give diagnosticians a "baseline" level of glucose in the bloodstream. The comparison of this reading to readings after consumption of food shows how well the pancreas is regulating the production of insulin and how effectively the insulin is regulating the distribution of glucose.
Blood Tests
Blood carries nourishment to cells and transports waste products away. The fluid that carries glucose carries red and white cells and other chemicals throughout the body is plasma. FBG tests, also called fasting plasma glucose tests, separate the plasma from the red cells and determine the concentration of glucose that it contains. Blood tests can also detect a number of other chemicals in the blood that give clues leading to diagnosis of many illnesses and conditions.
FBG Levels
Patients with healthy endocrine systems will have a fasting blood glucose level of less than 100 milligrams per liter. As of 2010, the American Diabetes Association considers a level of 70 to 99 milligrams per liter a normal fasting glucose level and readings from 100 to 140 milligrams per liter to be evidence of impaired fasting glucose. An elevated FBG level is indicative of a pre-diabetic condition. A highly elevated reading of 126 milligrams per liter or more on successive FBG tests alerts doctors to the development of Type 2 diabetes.
