Diabetes mellitus is a condition in which the level of glucose (sugar) in an individual's blood becomes too high because the body cannot use it properly. There are two common forms of diabetes. Type 1 diabetes is due to destruction of the insulin producing islets in the pancreas. Type 2 diabetes is due to the pancreatic islets failing after many years of increased insulin production because of resistance to the action of insulin in many tissues of the body, especially in muscle.
Insulin is a hormone, produced by the pancreas, which controls the movement of glucose into most of the body's cells and maintains blood glucose levels within a narrow concentration range. Most tissues in the body rely on glucose for energy production, and all but a few - such as the brain and nervous system - are entirely reliant on insulin to deliver this essential fuel.
Diabetes disrupts the normal balance between insulin and glucose. Usually after a meal, carbohydrate are broken down into glucose and other simple sugars. This causes blood glucose levels to rise and stimulates the pancreas to release insulin into the bloodstream. Insulin allows glucose into the cells, where it also promotes storage of excess glucose - either as glycogen in the liver or as triglycerides in adipose (fat) cells. If there is insufficient or ineffective insulin, glucose levels remain high in the bloodstream and the body's cells ‘starve’.
This can cause both short term and long term problems depending on the severity of the imbalance. In the short term it can upset the body's electrolyte balance, causing dehydration as high blood glucose levels increase the amounts of urine passed. If unchecked, this can eventually lead to loss of consciousness, kidney failure and death. Over time, high glucose levels can damage blood vessels, nerves and organs throughout the body, contributing to other problems such as high blood pressure and heart disease in addition to diabetes.