What is glucose?
Glucose comes from the Greek word for "sweet." It's a type of sugar you get from foods you eat, and your body uses it for energy. As it travels through your bloodstream to your cells, it's called blood glucose or blood sugar.

Every cell of the human body requires energy to perform the metabolic functions that sustain life. Glucose is a small, simple sugar that serves as a primary fuel for energy production, especially for the brain, muscles and several other body organs and tissues. Glucose also serves as a building block for larger structural molecules of the body, such as glycoproteins and glycolipids. The human body tightly regulates glucose levels. Abnormally high or low levels result in serious, potentially life-threatening complications.

Brain Fuel
The brain normally relies almost exclusively on glucose to fuel its energy needs. Because of its high energy demands and inability to store glucose, the brain requires a constant supply of the sugar. The body possesses multiple mechanisms to prevent a significant drop in blood glucose, or hypoglycemia. Should such a drop occur, however, brain functions can begin to fail. Common brain-related symptoms of hypoglycemia include headache, dizziness, confusion, lack of concentration, anxiety, irritability, restlessness, slurred speech and poor coordination. A sudden, severe drop on blood glucose can lead to seizures and coma.
Muscle Fuel
The skeletal muscles normally constitute approximately 30 to 40 percent of total body weight, although this varies based on sex, age and fitness level. The skeletal muscles utilize large amounts of glucose during exercise. Unlike the brain, the skeletal muscles store blood sugar in the form of glycogen, which is quickly broken down to supply glucose during physical exertion. Muscle tissue also normally absorbs large amounts of glucose from the bloodstream during exercise. Although skeletal muscles can utilize fat-derived molecules for energy production, depletion of glucose stores during prolonged exercise can lead to sudden fatigue -- commonly known as bonking or hitting the wall.
Fuel for Other Tissues and Organs
The various organs and tissues of the body have the capacity to utilize different fuels. In addition to the brain and skeletal muscles, some other important organs and tissues also rely on glucose as their primary or sole fuel. Examples include the cornea, lens and retina of the eyes, and the red and white blood cells. Interestingly, although the cells of the small intestines are responsible for absorbing glucose from food and passing it into the bloodstream, they primarily use another molecule called glutamine for fuel. This leaves more glucose for other organs and tissues that are more reliant on the sugar.
Structural Roles
In addition to its role in energy production, the human body utilizes glucose along with other substances to manufacture other important structural molecules. For example, the glycoprotein collagen consists of a protein backbone plus simple sugars, including glucose. Collagen is an essential structural molecule found in skin, muscles, bones and other body tissues. Other glycoproteins play important roles in the development and maintenance of the nerves of the body. Glycolipids, which consist of fat and sugar building blocks, are fundamental components of the membranes that surround the individual cells of the body, as well as structures within these cells.

What is Insulin ?
Important hormone allows your body to use sugar (glucose).
Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Insulin helps keeps your blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia).

The cells in your body need sugar for energy. However, sugar cannot go into most of your cells directly. After you eat food and your blood sugar level rises, cells in your pancreas (known as beta cells) are signaled to release insulin into your bloodstream. Insulin then attaches to and signals cells to absorb sugar from the bloodstream. Insulin is often described as a “key,” which unlocks the cell to allow sugar to enter the cell and be used for energy.
After you eat, cells in your pancreas are signaled to release insulin into the bloodstream.
If you have more sugar in your body than it needs, insulin helps store the sugar in your liver and releases it when your blood sugar level is low or if you need more sugar, such as in between meals or during physical activity. Therefore, insulin helps balance out blood sugar levels and keeps them in a normal range. As blood sugar levels rise, the pancreas secretes more insulin.
If your body does not produce enough insulin or your cells are resistant to the effects of insulin, you may develop hyperglycemia (high blood sugar), which can cause long-term complications if the blood sugar levels stay elevated for long periods of time...read more