Diabetes mellitus


Updated April 2008

Diabetes mellitus is an inability of the body to use glucose for energy due to either inadequate amounts of insulin (type 1 diabetes), or loss of sensitivity to the hormone insulin (type 2 diabetes). It is one of the most common long-term diseases occurring in the UK.

Normally, insulin is produced by the pancreas and enables the body’s cells to absorb the sugar glucose (their main energy source) from the blood. In diabetes mellitus, the cells cannot obtain glucose and so have to use other sources of energy, eg from the breakdown of fats, leading to a build-up of toxic by-products in the body.

In 2006, it was estimated that 2.2 million people in the UK had diagnosed diabetes. Type 2 diabetes is by far the most common form of diabetes, affecting over 1.8 million people in the UK. Although it is estimated that as many as half a million people have undiagnosed diabetes.[see reference 1] Diabetes becomes more common as people get older. While type 1 usually appears before the age of 40, the more common type 2 usually appears in people over the age of 40.[see reference 2]

In type 2 diabetes, the pancreas continues to secrete insulin, but the cells of the body become resistant to its effects. Often known as mature onset diabetes, this mainly affects people over the age of 40 and is more common in people who are overweight. In the initial stages, dietary measures may be sufficient to control the condition, but oral drugs and sometimes insulin injections become necessary as it progresses. The causes of type 2 diabetes are not well understood, but genetics and obesity are important factors. About one in three affected people have a relative with the same type of diabetes.

The symptoms of type 2 may not be obvious and may go unnoticed until a routine medical check-up. The main symptoms of both forms may include:
  • excessive passing of urine
  • thirst and a dry mouth
  • insufficient sleep because of the need to pass urine at night
  • lack of energy
  • blurred vision.
For anyone with diabetes mellitus, the aim of treatment is to maintain the level of glucose in the blood within the normal range without marked fluctuations. This aim may be achieved with dietary measures, a combination of diet and insulin injections, or diet and pills that lower blood glucose levels.

Diabetes mellitus may give rise to both short-term and long-term complications. A common complication of insulin treatment for either type of diabetes is hypoglycaemia in which blood sugar falls to abnormally low levels. Hypoglycaemia is often caused by an imbalance between food intake and the dose of insulin. The disorder is more common in people with type 1 but may also affect people with type 2 diabetes who take sulphonylurea drugs or insulin. If left untreated, hypoglycaemia can cause unconsciousness and seizures.

Certain long-term problems pose the main health threat to people with diabetes and may eventually affect even people whose diabetes is well controlled. Close control of blood sugar reduces the risk of developing these problems, and early recognition of complications helps in their control. Type 2 diabetes is often not diagnosed until years after its onset. As a result, complications may be evident at the time of initial diagnosis.

People who have diabetes are at increased risk of cardiovascular disorders. Large blood vessels may be damaged by atherosclerosis, which is a major cause of coronary artery disease and stroke. Other long-term complications result from damage to the small blood vessels throughout the body. Damage to blood vessels in the light-sensitive retina at the back of the eye may cause visual impairment (diabetic retinopathy). Diabetes also increases the risk of developing cataracts.

If diabetes affects blood vessels that supply nerves, it may cause nerve damage. There may be a gradual loss of sensation, starting with the hands and feet and sometimes gradually extending up the limbs.

Symptoms may also include dizziness upon standing and impotence in men. Loss of feeling, combined with poor circulation, makes the feet and legs more susceptible to ulcers and gangrene.

Damage to small blood vessels in the kidneys may also lead to further complications. Damage to the nerves controlling the body's internal functions ("autonomic neuropathy") can lead to problems with low blood pressure on standing (postural hypotension) or disturbance of the gastrointestinal tract (vomiting or diarrhoea), and increases the risk of sudden cardiac death.

Older people with diabetes need to see their doctor on a regular basis, and attend six monthly clinics to have their eyes and feet monitored for any degenerative changes.

All those with diabetes should have any vascular risk factors assessed and treated appropriately.

Many people with type 2 diabetes can control their blood glucose levels by taking exercise regularly and by following a healthy diet to maintain ideal weight. Advice can be provided by a dietician on the importance of low fat intake, and obtaining energy from complex carbohydrates with a low glycaemic index (such as wholemeal bread and brown rice) to minimise fluctuations in the blood glucose level.

In some frail older diabetics the priority of treatment should not be the tight control of blood sugar or prevention of complications, but the maximising of quality of life and the avoidance of symptoms of high blood sugar (thirst, lethargy, increased urination) or low blood sugar (hypoglycaemia) caused by treatment.

Further information on the epidemiology, aetiology and clinical management of diabetes can be found in the 2004 BMA Board of Science report Diabetes mellitus: an update for healthcare professionals.

References:
  1. Diabetes UK (2006) Diabetes: state of the nations 2006 - progress made in delivering the national diabetes frameworks. London: Diabetes UK.
  2. Diabetes UK with the All-Party Parliamentary Group for Diabetes (2005) Diabetes: state of the nations 2005 - progress made in delivering the national diabetes frameworks. London: Diabetes UK.
Further information:

© British Medical Association 2008

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