Blood glucose level refers to the amount of sugar present in a person's blood. Glucose is a necessary component of the human body that serves as the body's primary energy source. It is required for the proper function of a variety of tissues, including the brain. The morning before breakfast, blood sugar levels are low, and they rise following. The body's blood glucose level is continuously monitored to ensure that it remains constant at all times. Hyperglycemia is characterised by chronically high blood sugar levels, while hypoglycemia is characterised by persistently low blood sugar levels. Diabetes is caused by persistent hyperglycemia.