What is Fasting Blood & Urine Glucose?
Glucose (commonly called “blood sugar”) is the primary energy source for the body’s cells and the only short-term energy source for the brain and nervous system. A steady supply must be available for use, and a relatively constant level of glucose must be maintained in the blood. Glucose tests measure the level of glucose in your blood or detect glucose in your urine.
A few different protocols may be used to evaluate glucose levels. Fasting blood glucose (commonly called fasting blood sugar) test measures the blood glucose level after a fast of at least 8 hours. Urine is tested for glucose levels in urine as part of this diabetic panel.
During digestion, the carbohydrates that you eat are broken down into glucose (and other nutrients). They are absorbed by the digestive tract, move into the blood, and circulate throughout the body. Normally, blood glucose rises slightly after a meal and the hormone insulin is released by the pancreas into the blood in response. The amount of insulin released corresponds to the size and content of the meal. Insulin helps transport glucose into the body’s cells, where it is used for energy. As glucose moves into the cells and is broken down (metabolized), the blood glucose level drops and the pancreas responds by decreasing the release of insulin.
If this glucose/insulin blood feedback system is working properly, the amount of glucose in the blood remains fairly stable. If the feedback system is disrupted and the glucose level in the blood rises, then the body tries to restore the balance by increasing insulin production.
Diabetes is the most common disease resulting from an imbalance between glucose and insulin.
- Type 1 diabetes results when the body is not able to produce sufficient insulin to control blood glucose levels. Usually, in type 1 diabetes, the cells that produce insulin (beta cells) have been destroyed by the person’s own immune system.
- Type 2 diabetes results from a combination of insulin resistance (the body does not react normally to insulin) and a relative decline in insulin production.
- Some women may develop gestational diabetes, which is high blood glucose that develops during pregnancy.
Severe, acute changes in blood glucose, either high (hyperglycemia) or low (hypoglycemia), can be life-threatening, causing organ failure, brain damage, coma, and, in some cases, death. Chronically high blood glucose levels that can occur with untreated or poorly controlled diabetes can cause progressive damage to body organs such as the kidneys, eyes, heart and blood vessels, and nerves. Chronic hypoglycemia can lead to brain and nerve damage.
How is the test used?
Screening and Diagnosis
Fasting Blood and Urine Glucose - this test may be used to screen for and diagnose prediabetes and diabetes in people with signs and symptoms. In some cases, there may be no early signs or symptoms of diabetes, so this test may be used to screen people at risk of diabetes. Screening can be useful in helping to identify it and allowing for treatment before the condition worsens or complications arise. If the initial screening result is abnormal, the test should be repeated. The repeat result must also be abnormal to confirm a diagnosis of diabetes. Certain other tests (e.g., HbA1c) can also be used to confirm the diagnosis of diabetes.
Some people with diabetes must monitor their blood glucose levels, as directed by the physician, to determine how far above or below normal their glucose is and to determine what medications or insulin(s) they may need.