Diabetes explained

Diabetes mellitus is a condition in which bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. levels of glucoseA simple sugar that is an important source of energy in the body., the sugar used as fuel by the body, are increased. This may be caused by a lack of the hormoneA substance produced by a gland in one part of the body and carried by the blood to the organs or tissues where it has an effect. insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels., or by a failure of the body to respond to insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels..

For convenience, diabetes mellitusDisordered energy metabolism and high levels of glucose in the blood owing to a lack of insulin, or poor response of the body to insulin. will be referred to simply as 'diabetes' from here on.

Because the kidneys can filter out only a certain amount of glucoseA simple sugar that is an important source of energy in the body. from the urine, when bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. glucoseA simple sugar that is an important source of energy in the body. levels become high enough, glucoseA simple sugar that is an important source of energy in the body. also appears in the urine.

There are several different types of diabetes, but all are characterised by the following features:

  • High levels of glucoseA simple sugar that is an important source of energy in the body. in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. - hyperglycaemiaA high level of glucose in the blood.
  • Glucose in the urine - glycosuriaAbnormally high levels of glucose in the urine..[1]

These features are responsible for the symptoms of diabetes, and for the complications that often develop over the years.[1]

What does insulin do?

Insulin is a hormoneA substance produced by a gland in one part of the body and carried by the blood to the organs or tissues where it has an effect. that is produced in the pancreas by cells called beta cellsThe cells of the pancreas where insulin is produced.. The main effect of insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels. is to lower bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. glucoseA simple sugar that is an important source of energy in the body. levels. It promotes the uptake of glucoseA simple sugar that is an important source of energy in the body. by body cells, allowing it to be used as fuel. It also stimulates the body to convert glucoseA simple sugar that is an important source of energy in the body. into fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body., and inhibits glucoseA simple sugar that is an important source of energy in the body. production from the breakdown of fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. and protein.[1]

One of the main concerns for people with diabetes is the development of complications - for example, heart disease - that result from having high bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. glucoseA simple sugar that is an important source of energy in the body. over many years. Fortunately, diabetes can now be managed effectively, and closely controlling bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. glucoseA simple sugar that is an important source of energy in the body. levels reduces the risk of complications developing.[1,2]

Learn more about the complications of diabetes.

Types of diabetes

The two main forms of diabetes are type 1 and type 2 diabetes.

  • Type 1 diabetes is mainly caused by a reduction in insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels. levels, sometimes to the point where insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels. is totally lacking
  • Type 2 diabetes is largely due to insulin resistanceA reduced response of the body to the hormone insulin, resulting in raised blood glucose levels..

Some women develop diabetes when they are pregnant; this is called gestational diabetesAny level of glucose intolerance first detected during pregnancy.. It usually disappears after the birth, although these women have a higher risk of developing type 2 diabetes later in life.[1,2]

Diabetes may also be caused by other conditions: for example, diseases of the pancreas, such as pancreatitis. In addition, some medicines may increase the risk of diabetes; these include steroids and the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure-lowering medications, thiazides.[2]

See more detail about type 1 and type 2 diabetes.

References: 
  1. Boon NA, Colledge NR and Walker BR. Davidson's Principles and Practice of Medicine Churchill Livingstone Elsevier. 2006; 20th edition
  2. Longmore M, Wilkinson I and Török E. Oxford Handbook of Clinical Medicine 2002; 5th edition