The doctor or health care provider wants you to measure how much glucose, a type of sugar, is in your blood. It is often called blood sugar. For the body to have the energy to work right, blood glucose needs to be balanced. Too much glucose, called hyperglycemia, can cause harm to the body over time. Too little, called hypoglycemia can cause a person to get very sick, very fast. When hypoglycemia happens, it must be treated right away.