The bloodstream carries glucose which is a type of sugar produced from the digestion
of carbohydrates and other foods. Glucose provides energy to cells throughout
the body. Unused glucose is stored mainly in the liver as glycogen.
Insulin, glucagon and other hormone levels rise and fall to maintain a normal
range of blood sugar levels. Too little or too much of these hormones can cause
blood sugar levels to fall too low (hypoglycemia) or rise too high (hyperglycemia
Normally, blood glucose levels increase slightly after a meal. When blood sugar
rises, cells in the pancreas release insulin, which causes the body to absorb
glucose from the blood, thus lowering the blood sugar level to normal. When
blood sugar drops too low, the level of insulin declines and other cells in
the pancreas release glucagon, which causes the liver to turn stored glycogen
back into glucose and release it into the blood. This brings blood sugar levels
back up to normal.