Blood sugar is the amount of glucose present in the blood. It provides the body with energy, but too little or too much can cause health problems. Blood sugar can be measured a few different ways. A fasting blood glucose test is performed after eight hours of not eating. A random blood glucose test can be done anytime to check sugar levels.
Both tests may be done to help diagnose a medical condition. For example, most pregnant women are screened for gestational diabetes. Random blood sugar checks are also done by people who need to keep a close eye on their sugar level.
Normal results for a fasting blood sugar test are 70 to 100 mg/dl (milligrams per deciliter). In a test done without fasting, normal blood sugar levels are between 70 and 140 mg/dl. If levels are below 70 mg/dl, the condition may be referred to as hypoglycemia, meaning low blood sugar. When the levels are higher than 140 with a non-fasting test, the condition may be called hyperglycemia.
Blood sugar can be tested from a small amount of blood drawn. Although tests can be performed at a hospital or lab, small home glucose monitoring devices are available. A small amount of blood is obtained, usually through a finger stick, and placed in a meter which calculates glucose levels and provides a digital readout in only a few seconds.