Diabetes is categorized into two types; type 1 and type 2. Both types of diabetes are categorized by a disorder of insulin production, usage of insulin in the body, or both. The pancreas secretes insulin, a hormone, which is responsible for moving glucose (sugar in the blood) into cells of the body. This process is triggered when a high level of glucose is present in the bloodstream. The liver and the muscles receive signals to store glucose away as glycogen. Insulin "tells" the cells to store glucose in the form of fat, to reserve energy for future usage. Insulin receptors are found in all cells throughout the body. Blood glucose levels are normally stable in a healthy individual.
Type 1 diabetes, which has also been known as insulin-dependent diabetes, is considered a progressive autoimmune disease, in which the beta cells that produce insulin are slowly destroyed by the body's own immune system. It is unknown what initiates this process. Evidence suggests that both a genetic predisposition and environmental factors, such as a viral infection, are involved in causing the condition. Insulin replacement therapy is usually required as the body no longer produces any insulin.
Type 2 diabetes is the most common form of diabetes, accounting for 90 – 95% of cases. In type 2 diabetes, the body does not respond properly to insulin, a condition known as insulin resistance. Over time, the pancreas may become exhausted and unable to produce insulin in adequate amounts. The disease is progressive and several stages occur. Insulin and glucose levels will be elevated during the early stages, while in the later stages insulin levels drop and blood glucose levels are raised. Treatment of type 2 diabetes should be adapted to the specific stage of the disease present.