Blood sugar, or glucose, is an important source of energy and provides nutrients to your body's organs, muscles and nervous system. The body gets glucose from the food you eat, and the absorption, storage and production of glucose is regulated constantly by complex processes involving the small intestine, liver and pancreas.
Normal blood sugar varies from person to person, but a normal range for fasting blood sugar (the amount of glucose in your blood six to eight hours after a meal) is between 70 and 100 milligrams per deciliter. For most individuals, the level of glucose in the blood rises after meals. A normal blood-sugar range after eating is between 135 and 140 milligrams per deciliter.
These variations in blood-sugar levels, both before and after meals, are normal and reflect the way that glucose is absorbed and stored in the body. After you eat, your body breaks down the carbohydrates in food into smaller parts, including glucose, which can be absorbed by the small intestine.
As the small intestine absorbs glucose, the pancreas releases insulin, which stimulates body tissues and causes them to absorb this glucose and metabolize it (a process known as glycogenesis). This stored glucose (glycogen) is used to maintain healthy blood-sugar levels between meals.
When glucose levels drop between meals, the body takes some much-needed sugar out of storage. The process is kicked off by the pancreas, which releases a hormone known as glucagon, which promotes the conversion of stored sugar (glycogen) in the liver back to glucose. The glucose is then released into the bloodstream.
When there isn't enough glucose stored up to maintain normal blood-sugar levels, the body will even produce its own glucose from noncarbohydrate sources (such as amino acids and glycerol). This process, known as gluconeogenesis, occurs most often during intense exercise and instances of starvation.
While it may seem complicated (and it is), there's a good reason for your body to keep up this never-ending dance with glucose: Too much or too little glucose in the blood can lead to serious health problems.
Too much glucose over an extended time (hyperglycemia) can result in the destruction of nerves, lowered resistance to infection, and heart and kidney disease. On the other hand, not enough glucose in the blood over an extended period (hypoglycemia) can affect brain function, causing fatigue, fainting, irritability and, in some cases, seizures and loss of consciousness.