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Blood Glucose Test

Test Overview

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods. It is the main source of energy used by the body. Insulin is a hormone that helps your body's cells use the glucose. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.

Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.

There are several different types of blood glucose tests.

  • Fasting blood sugar (FBS) or fasting blood glucose (FBG) measures blood glucose after you have not eaten for at least 8 hours. It is often the first test done to check for prediabetes and diabetes.
  • Random blood sugar (RBS) or random blood glucose (RBG) measures blood glucose regardless of when you last ate. Several random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day. Blood glucose levels that vary widely may mean a problem. This test is also called a casual blood glucose test.
  • A 2-hour postprandial blood sugar test measures blood sugar exactly 2 hours after you start eating a meal. This test is most often done at home when you have diabetes. It can see if you are taking the right amount of insulin with meals.
  • The hemoglobin A1c test and the oral glucose tolerance test (OGTT) are other tests used to look at blood sugar levels. The A1c test can be used to estimate your average blood sugar level over the past 2 to 3 months. The OGTT is commonly used to diagnose diabetes that occurs during pregnancy (gestational diabetes).
Information about Blood Glucose Test

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Information about Blood Glucose Test

Adaptation Date: 2/24/2022

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services