Glucose is a monosaccharide and thus a simple sugar. In the human body, glucose is the most important energy supplier. The human brain consumes about 75% of the ingested glucose daily, which is about 200g for an adult. Measuring blood glucose levels is the most important indicator for diagnosing diabetes mellitius. Glucose level is also of great importance for monitoring the course of similar diseases. In addition to measurement in blood, the monosaccharide can also be checked in body fluids such as urine. To get a real and honest result about the blood glucose level, it is important that the patient is fasting at the time of measurement.