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What is M.E.

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Information covering:

What does M.E. feel like?

Range of symptoms

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'What you need to know about M.E.'

M.E. Association factsheet 

Also available as a free download

Information from the ME Association Factsheet

ME (myalgic encephalopathy or encephalomyelitis) is a complex multisystem disease with a wide range of disabling symptoms.


  • ME is classified by the World Health Organisation (WHO) as a neurological disease. WHO classification is recognised by the Department of Health, the Medical Research Council and NICE (National Institute for Health and Care Excellence).

  • ME is estimated to affect around 0.2 to 0.4 per cent of the population (approximately 250,000 people in the UK) — including children and adolescents.

  • ME affects all social classes and ethnic groups.

  • ME is the commonest cause of long-term sickness absence from school.

  • ME can affect more than one family member — suggesting that genetic factors may be involved in predisposing people to develop the disease when a triggering event occurs.

  • ME has been estimated to cost the UK economy £3.3bn each year.

  • ME can cause greater functional impairment than many other serious medical conditions, including multiple sclerosis and cancer.

  • ME is a devastating disease with no established biomarker. Significant abnormalities in the central nervous system, immune system, endocrine (hormone producing) system, and in muscle (causing energy metabolism impairment), have all been found to be involved in the disease process.

  • ME is not a minor ailment and there is a wide spectrum of severity. Around 25 per cent of people are severely affected — being house-bound, or bed-bound and often requiring a wheelchair if they can mobilise — at various stages during the illness.

  • ME can affect some people very severely, leading to atypical seizures, speech and swallowing difficulties and extreme intolerance to light and sound. These people will be bedbound, require continuous 24-hour care and may require tube-feeding.

  • ME in most cases can be linked to a previous viral infection — from which people do not seem to have recovered. In some cases, ME can follow a vaccination, or other known triggering event.

  • ME is generally regarded as a fluctuating condition — meaning that the symptoms can vary in form and intensity throughout the day, from day to day, and week to week — making it very unpredictable.

  • ME is diagnosed following careful assessment of clinical history, physical examination, exclusion of other possible causes of symptoms and the application of diagnostic criteria. There are currently no blood or other diagnostic tests available.

  • ME has a unique and defining clinical feature known as post-exertional malaise — a delayed exacerbation of symptoms that can follow even minor physical or mental exertion.


The most important diagnostic symptoms are:

  • Exercise-induced muscle fatigue.

  • Post-exertional malaise/symptom exacerbation.

  • Cognitive dysfunction, that is, problems with short-term memory, concentration, attention span.

  • Unrefreshing sleep.

  • Ongoing flu-like symptoms including sore throats and enlarged glands.

  • Problems with pulse and blood pressure control leading to feeling faint and orthostatic intolerance — caused by autonomic nervous system dysfunction.


Other common symptoms include:

  • Pain — which can involve muscle, joints and nerves.

  • Problems with balance and temperature control.

  • Sensitivity to light and sound.

  • Alcohol intolerance.


Drugs can be used to help manage or control some symptoms such as pain and sleep disturbance.

There is no form of curative treatment at present — although several drugs are being assessed in clinical trials.

The most important aspect of treatment is activity management — which involves striking the right balance between activity and rest so as not to exacerbate symptoms. This is known as pacing.

Most people with ME will make some degree of improvement over time. However, a significant minority remain permanently and severely affected.

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