It is estimated that there are 17 million cases of ME/CFS worldwide. However, due to the lack of a medical biomarker for diagnosis it is more likely that numbers are increased. Current estimates in the UK suggest there are over 600,000 cases and counting. Estimates for the USA are around 5 million and estimates across the European Union suggest around 4 million.  

ME/CFS does not discriminate between age and gender as men, women and children are clinically diagnosed with the condition. However, around three times more women are affected then men.

The average age of adult onset is commonly between the early twenties and mid forties; although adults younger and older can develop this devastating disease.

The most common age for children to develop ME/CFS is between 13 – 15 years old, although there are many cases of children being diagnosed earlier. 

Each case of ME/CFS is different is aspects of severity. Categories include:


People presenting with mild ME/CFS may care for themselves and do light domestic tasks, but with difficulty. They are still likely to be able to do a job, but may often take days off work. In order to remain in work they are likely to have stopped most leisure and social activities. Weekends or other days off from work are used to rest in order to cope with the week ahead.


Moderate ME/CFS presents with reduced mobility which restricts most activities of daily living. The level of ability and severity of symptoms often varies from time to time (peaks and troughs). Most people affected at this level are likely to have stopped work, education and require rest periods during the day; often sleeping 1 -2 hours in the afternoon. Night-time sleep tends to be poor and disturbed.


People with severe CFS/M.E. are unable to do any activity for themselves, or can carry out minimal daily tasks only (such as face washing, cleaning teeth). They have severe cognitive difficulties and depend on a wheelchair for mobility. They are often unable to leave the house, or have a severe and prolonged after-effect if they do so. They may also spend most of their time in bed, and are often extremely sensitive to light and noise.

The above categories outline physical function with regard to severity. It is common for those affected with ME/CFS to experience fluctuations during the lifetime of their condition; moving from mild to moderate, moderate to severe and visa versa.

25 % of all cases present as Severe ME and require very careful management. Please visit the 25% ME Group for more detailed information on management and care of severe ME/CFS.