Most glucose tests use a blood sample to measure the amount of glucose (blood sugar) in a person’s bloodstream. Urine tests can also indicate the level of a person’s glucose but are less accurate than blood tests and rarely used for this purpose. Several versions of glucose tests are used to diagnose diabetes, monitor diabetes management or assess the progression of the disease.

Glucose is the major source of energy in the body. Most of the carbohydrates people eat are broken down into glucose before being absorbed into the bloodstream. In healthy individuals, a hormone called insulin carries the glucose to the cells, where it is converted into energy.

However, diabetic individuals either do not manufacture insulin in their bodies (type 1 diabetes) or cannot properly use the insulin they do create (type 2 diabetes and gestational diabetes). As a result, glucose stays in the bloodstream and builds up, a condition known as hyperglycemia. Excess glucose can lead to heart conditions, nerve damage, kidney disease, eye diseases and other serious health problems. Diabetic individuals can also experience bouts of hypoglycemia (low glucose), which can cause seizures and a diabetic coma.

Glucose tests allow physicians to measure how much glucose is in a patient’s bloodstream. These tests can be used to diagnose diabetes and to monitor its progression. Glucose tests reveal:

• How effectively the body is breaking down foods and converting glucose into energy
  
  
• How effectively the liver is working
  
  
• How effectively other organs are working, particularly those that help regulate glucose

In each test, a sample of blood is analyzed for its glucose content and compared to a range of blood glucose levels that indicate whether the patient’s results are within the normal range or indicate prediabetes or diabetes.

Different tests are available to check blood glucose. For example, some tests examine blood glucose after periods of fasting, whereas others check levels shortly after meals. The results describe how insulin and glucose are interacting in a patient.