The term hyperglycemia, which literally means “condition of too much sugar in the blood,” is used anytime the blood glucose concentration becomes higher than the normal set point level. Hyperglycemia is most often associated with untreated diabetes mellitus, but it can occur in newborns when too much intravenous glucose is given or in other similar situations. If untreated, the excess glucose leaves the blood in the kidney—literally “spilling over” into the urine. This increases the osmotic pressure of urine, drawing an abnormally high amount of water into the urine from the bloodstream. Thus hyperglycemia causes loss of glucose in the urine and its accompanying loss of water—potentially threatening the fluid balance of the body. Dehydration of this sort can ultimately lead to death.
In contrast, hypoglycemia occurs when the blood glucose concentration dips below the normal set point level. Hypoglycemia can occur in various conditions, including starvation, hypersecretion of insulin by the pancreatic islets, or injection of too much insulin. Symptoms of hypoglycemia include weakness, hunger, headache, blurry vision, anxiety, and personality changes—sometimes leading to coma and death if untreated.