Understanding blood glucose or blood sugar is a term that refers to the level of glucose in the blood . Blood sugar concentration , or serum glucose level , strictly regulated in the body . Which flowed through the blood glucose is the main source of energy for the body’s cells . Glucose is a monosaccharide , which is another term for simple sugars . It is one of three monosaccharides that are used by the body , but it is the only one that can be used directly to produce ATP . ATP is used by the body for energy , in fact , ATP is the only molecule that can be used for energy . Thus , sufficient glucose is very important .