Fasting glucose is a blood sugar measurement taken after no food has been eaten for at least 8 to 10 hours. A fasting blood sugar (FBS) test is usually the first kind used when a doctor orders testing for diabetes diagnosis. Diabetics can test their own fasting glucose before breakfast with a home blood sugar monitor.
Most diabetics record their blood sugar readings at different times each day to track their glucose levels overall during a given week. In addition to a fasting glucose, two hours after meals is another common time to check blood sugar levels. Many diabetic people eat five or six small meals throughout the day rather than three large ones to avoid causing big fluctuations in their blood sugars. Exercise can also affect blood sugar — usually causing it to lower. Fasting blood sugars should also be on the low side since there is no food in the body.
During diabetes diagnostic procedures, doctors first usually order an FBS test before having an oral glucose tolerance test (OGTT) conducted. While the FBS tests the body's fasting glucose on an empty stomach, the OGTT measures its reaction after drinking a controlled amount of sugary substance. The OGTT is usually performed several times in order to get an accurate result. A one-hour OGTT is routinely given to pregnant women to screen them for gestational diabetes. Gestational diabetes occurs in pregnancy and typically presents as high blood sugar levels.
A state of high blood sugar is called hyperglycemia, while a low glucose level is hypoglycemia. Diabetics may experience a wide range of sugar levels from high to low and this can be extremely dangerous. Drastically low or high glucose levels can cause medical problems or even coma and death. Understanding how the body reacts to taking in sugar as well as its fasting glucose level can help control wide fluctuations in blood sugars for better health outcomes.
FBS and OGTT differ from random blood sugar (RBS) tests. Unlike fasting glucose and sugar tolerance tests, the RBS checks blood sugars at any time. In non-diabetic people, blood sugar doesn't usually fluctuate as greatly as it does in many diabetics. Normal blood sugar levels are often considered to be about 100 ml or a little higher than that. The goal of monitoring fasting glucose as well as other sugar tests is to better control hyperglycemia, hypoglycemia and diabetes through awareness, diet and/or medication.