What Is a Fasting Blood Glucose Test?
A fasting blood sugar (FBS) or fasting glucose test measures blood sugar levels. Elevated levels are associated with diabetes and insulin resistance, in which the body cannot properly handle sugar. Your doctor will explain where your levels should be.
This test requires a 12-hour fast. You should wait to eat and/or take a hypoglycemic agent (insulin or oral medication) until after blood for the test has been drawn, unless told otherwise.
Eating and digesting carbohydrates forms glucose (blood sugar). Glucose is needed by your body to provide energy to carry out your normal activities. Insulin is needed by the body to allow glucose to go into the ce3lls and be used as energy. Without insulin, the levels of glucose in the blood will rise. Diabetes is a disease that occurs when either the pancreas is not able to produce insulin or the pancreas makes insulin, but it does not work as it should or does not make enough to keep blood glucose in a normal range. Fasting blood sugar is a part of diabetic evaluation and management. An FB greater than 126 mg/dL on more than one occasion usually indicates diabetes.
–Source: Cleveland Clinic