A blood glucose test is a blood test that screens for diabetes by measuring the level of glucose (sugar) in a person’s blood.
The following categories of people are considered "high-risk" candidates for developing diabetes:
In addition to testing the above individuals at high risk, the American Diabetes Association also recommends screening all individuals age 45 and older.
Your body converts sugar, also called glucose, into energy so your body can function. The sugar comes from the foods you eat and is released from storage from your body’s own tissues.
Insulin is a hormone made by the pancreas. Its job is to move glucose from the bloodstream into the cells of tissues. After you eat, the level of glucose in the blood rises sharply. The pancreas responds by releasing enough insulin to handle the increased level of glucose — moving the glucose out of the blood and into cells. This helps return the blood glucose level to its former, lower level.
If a person has diabetes, two situations may cause the blood sugar to increase:
As a result of either of these situations, the blood sugar level remains high, a condition called hyperglycemia or diabetes mellitus. If left undiagnosed and untreated, the eyes, kidneys, nerves, heart, blood vessels and other organs can be damaged. Measuring your blood glucose levels allows you and your doctor to know if you have, or are at risk for, developing diabetes.
Much less commonly, the opposite can happen too. Too low a level of blood sugar, a condition called hypoglycemia, can be caused by the presence of too much insulin or by other hormone disorders or liver disease.
To get an accurate plasma glucose level, you must have fasted (not eaten or had anything to drink except water) for at least 8 hours prior to the test. When you report to the clinic or laboratory, a small sample of blood will be taken from a vein in your arm. According to the practice recommendations of the American Diabetes Association, the results of the blood test are interpreted as follows:
*Values between 50 and 70 are often seen in healthy people
**The condition of "prediabetes" puts you at risk for developing Type 2 diabetes, high blood pressure, and blood lipid disorders
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 02/21/2018