Glucose is a simple sugar, also known as a monosaccharide, that circulates in the bloodstream, providing all cells in the body with the fuel they need for essential functions. A glucose assay, sometimes called a glucose test, is the process of analyzing a substance to determine if it contains glucose, and if so in what concentration. In medicine, this assay is most commonly used to measure the concentration of glucose in the body to diagnose and manage metabolic problems, such as diabetes. Samples of either urine or blood can be used to do medical glucose tests, but the serum derived from blood samples gives the most accurate results. There are several different ways to perform a glucose assay, but the two main types are chemical assays, which are relatively cheap and easy to perform, and the newer enzymatic assays, which are more accurate but also require more time and resources.
Doctors most often perform glucose assays to diagnose diabetes, hyperglycemia, or high blood glucose levels, and hypoglycemia, or low blood glucose levels. One common test done for this purpose is called a glucose tolerance test. In this test, the glucose test is done to analyze how quickly a certain amount of glucose is metabolized by the body. A fasting blood sugar test can also be used for similar purposes. It assays the glucose level in the blood after 12 hours of fasting and is commonly done to test for gestational diabetes.
Monitoring glucose levels in people diagnosed with diabetes is another common use for glucose assays. A person with diabetes has higher than normal levels of glucose which can lead to serious disease and death. To help maintain a normal blood glucose level, a small blood sample is taken frequently and a glucose assay is used to determine the concentration of glucose in the blood. A glucose meter is often used to perform this test. Glucose assays can also be performed for non-medical purposes, for example to analyze the sugar content of plant extracts and of various goods in the food industry.
The most common chemical method of performing a glucose assay is the dinitrosalicylic acid (DNS) assay, which was first introduced in 1955. More accurate enzymatic glucose assay methods have been developed and are more commonly used in medicine today. Enzymatic assays use various reactive compounds called reagents to determine glucose levels. A common reagent used is glucose oxidase, a substance usually extracted from certain species of mold.