Insulin is a protein that the body synthesizes. The human body utilizes insulin to transport glucose from the bloodstream into the body's cells. The cells can then utilize the glucose for energy and to undergo all of their cellular processes.
Insulin is also known as a hormone and is produced by the pancreas. Patients who have diabetes either do not synthesize enough insulin to combat their diets or do not respond to insulin properly.
Because insulin is a protein, it cannot be taken orally by diabetic patients. Proteins are digested in the stomach and, if taken orally, insulin degrades and does not make it to the bloodstream.