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Chronic fatigue syndrome

Myalgic encephalomyelitis

Chronic fatigue syndrome (CFS), previously sometimes known as myalgic encephalomyelitis (ME), is a condition where there is long-term disabling tiredness (fatigue). Most people with also have one or more other symptoms such as muscular pains, joint pains, disturbed sleep patterns, poor concentration or headaches. The cause is not known.

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What is chronic fatigue syndrome?

Chronic fatigue syndrome (CFS), which was sometimes previously referred to as myalgic encephalomyelitis (ME), is a condition that causes marked long-term tiredness (fatigue) and other symptoms which are not caused by any other known medical condition.

How long does chronic fatigue syndrome last?

Chronic fatigue syndrome is a fluctuating condition in which symptoms can change unpredictably in nature and severity over time. The impacts are variable in severity but there can be flare-ups and relapses even if symptoms are generally well managed.

There is no test to diagnose the condition. The diagnosis is made in people who have a certain set of symptoms.

What are the symptoms of chronic fatigue syndrome?

The onset of chronic fatigue syndrome symptoms can be fairly sudden (over a few days or so), or more gradual. Chronic fatigue syndrome should be suspected if the following symptoms are not explained by any other condition, and persist for a minimum of six weeks in adults, or four weeks in children and young people:

  • Extreme tiredness (fatigue) that is worsened by activity, but is not caused by excessive exertion and is not significantly relieved by rest.

  • Post-exertional malaise (PEM): feeling unwell with no energy after activities, with a worsening of symptoms that:

    • Often doesn't start until hours or days after the activity.

    • Is much greater than expected for that particular activity.

    • Has a prolonged recovery time that may last hours, days, weeks or longer.

  • Unrefreshing sleep problems or sleep disturbance, which may include:

    • Feeling exhausted, feeling flu-like and stiff on waking.

    • Broken or shallow sleep, altered sleep pattern or excessive daytime sleepiness (hypersomnia).

  • Difficulties with conscious physical or mental activities, such as thinking, reasoning, or remembering (cognitive difficulties), sometimes described as 'brain fog'. This may include:

    • Problems finding words or numbers.

    • Difficulty in speaking.

    • Slow to respond.

    • Short-term memory problems.

    • Difficulty concentrating or multitasking.

  • Inability to engage fully in work, educational, social or personal activities is a common symptom.

The diagnosis can only be confirmed after three months of persistent long-term symptoms and only if the symptoms cannot be explained by any other condition.

Other chronic fatigue syndrome symptoms

Other symptoms that may be associated with CFS include:

  • Dizziness, palpitations, fainting, nausea on standing or sitting upright from a lying position.

  • Increased sensitivity to temperature, causing increased sweating, chills, hot flushes or feeling very cold.

  • Flu-like symptoms, including sore throat, tender glands, nausea, chills or muscle aches.

  • Intolerance to alcohol, or to certain foods or chemicals.

  • Increased sensitivities, including to light, sound, touch, taste and smell.

  • Pain, including pain on touch, muscle pain, headaches, eye pain, tummy (abdominal) pain, or joint pain.

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Severity of chronic fatigue syndrome symptoms

Symptoms vary widely in severity and people may have some symptoms more severely than others. However, the following definitions are provided by NICE to provide a guide to the level of impact of symptoms on everyday functioning:

Mild chronic fatigue syndrome

  • Able to care for oneself and do some light domestic tasks (sometimes needing support) but may have difficulties with mobility.

  • Able to work or attend education but to do this have probably stopped all leisure and social pursuits.

  • Often have reduced hours, take days off and use the weekend to cope with the rest of the week.

Moderate chronic fatigue syndrome

  • Reduced mobility and restrictions in all activities of daily living.

  • May have peaks and troughs in level of symptoms and ability to do activities.

  • Have usually stopped work or education and need rest periods, often resting in the afternoon for one or two hours.

  • Sleep at night is generally of poor quality and disturbed.

Severe chronic fatigue syndrome

  • Unable to do any activity for oneself, or can carry out minimal daily tasks only (such as face washing or cleaning teeth).

  • Severe cognitive difficulties and may depend on a wheelchair for mobility.

  • Often unable to leave the house or have a severe and prolonged after-effect if you do so.

  • May also spend most of the time in bed and often extremely sensitive to light and sound.

Very severe chronic fatigue syndrome

  • In bed all day and dependent on care.

  • Need help with personal hygiene and eating and are very sensitive to sensory stimuli.

  • Some people with very severe CSF may not be able to swallow and may need to be tube fed.

How is chronic fatigue syndrome diagnosed?

There is currently no test to aid diagnosis of CFS and it is recognised from symptoms alone. However, some tests are usually done to rule out other causes of tiredness or other symptoms.

For example, blood tests may be done to rule out any other medical conditions such as anaemia, an underactive thyroid gland, liver problems and kidney problems.

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What causes chronic fatigue syndrome?

The cause of chronic fatigue syndrome is not known. There are various theories but none has been proved.

A popular theory is that a viral infection may trigger the condition. Tiredness (fatigue) is a common symptom that can persist for a short time following certain viral infections. For example, infection with the glandular fever virus or the influenza virus can cause fatigue for several weeks after other symptoms have gone. However, most people recover within a few weeks from the tiredness that follows known viral infections.

Even if a viral infection is a trigger of CFS, it is not clear why symptoms persist when there is no evidence of persisting infection. Also, many people with CFS do not have an initial viral infection.

Factors that are thought to contribute to some people developing CFS include:

  • Inherited genetic susceptibility (it is more common in some families).

  • Mental stress.

  • Depression.

  • A traumatic event such as bereavement, divorce or redundancy.

It is hoped that research will clarify the cause (or causes) of CFS in the future.

Who develops chronic fatigue syndrome?

Chronic fatigue syndrome can affect anyone. It is estimated that CFS affects an average of between one and five people in every 1,000 in the UK. The true figure may be higher because some people with CFS are not diagnosed.

It is about three times as common in women as in men. The most common age for it to develop sometime between the early twenties and mid-forties. In children the most common age for it to develop is 13-15 years but it can develop at an earlier age.

Treating chronic fatigue syndrome

There is no known cure for chronic fatigue syndrome although symptoms can be self-managed with support and advice. When CFS is suspected, a diagnosis will be made by a specialist CFS clinic which will also give individual advice about managing the symptoms. This medical advice will usually include:

  • Trying to manage daily activities, not using excess energy and not 'pushing through' any symptoms.

  • Resting as needed. This might mean making changes to a daily routine, including work, school and other activities.

  • Maintaining a healthy balanced diet with adequate fluid intake.

Children and young people with symptoms of CFS should be referred to a paediatrician for further assessment and investigation before referral to a paediatric chronic fatigue syndrome specialist team to confirm the diagnosis and develop a care and support plan.

Energy management

Each person has a different and fluctuating energy limit and individuals tend to be the expert in judging their own limits.

A personalised physical activity or exercise programme should only be considered if people feel ready to progress their physical activity beyond their current activities of daily living or would like to include physical activity or exercise into managing their CFS.

Some people with chronic fatigue syndrome have found that energy management programmes can make their symptoms better, some people find it makes no difference and others find them unhelpful.

An energy management plan for chronic fatigue syndrome uses a flexible approach that is tailored individually so that activity is never automatically increased but is maintained or adjusted (upwards after a period of stability or downwards when symptoms are worse). Energy management can take weeks, months or sometimes even years to reach stabilisation or to increase tolerance or activity.

An energy management plan includes all types of activity (mental, physical, emotional and social) and takes into account the overall level of activity. It helps people learn to use the amount of energy they have whilst reducing the risk of post-exertional malaise or worsening symptoms of chronic fatigue syndrome by exceeding energy limits.

Any activity or exercise programme must be led by the individual, with support from a healthcare professional in an CFS specialist team. A physical activity or exercise programme should be overseen by a physiotherapist in an CFS specialist team.

The first step is to agree a sustainable level of activity, which may mean initially reducing activity. This plan should include periods of rest and activity. It is important to alternate and vary between different types of activity and to break activities into small chunks.

Exercise that is not part of the programme, such as going to the gym, should be avoided because this may worsen symptoms. Graded exercise therapy in which you make fixed increases in the time spent being physically active is no longer recommended in CFS.

Cognitive behavioural therapy

Cognitive behavioural therapy (CBT) can be offered to help people manage their symptoms, improve their level of functioning and reduce the distress associated with having a chronic illness.

CBT for people with CFS aims to improve quality of life.

CBT should aim to help people develop an understanding about the main difficulties and challenges they face, explore their understanding of their symptoms and illness and so help to manage symptoms.

Severe or very severe CFS/ME

People with severe or very severe CFS/ME will need more frequent reviews and increased support and care. They should also be referred:

  • To a physiotherapist or occupational therapist working in an CFS specialist team for support on developing energy management plans.

  • To a dietician with a special interest in CFS.

The process and pace of any CBT should be adjusted to meet their needs. This might include shorter, less frequent sessions and longer-term goals.

Flare-ups and relapse of chronic fatigue syndrome

Flare-ups and relapses can happen even if the symptoms are generally well-managed. It is very important that people are given and agree individual advice on how to adjust their activity during a flare-up or relapse. This should include how to access review and support from a physiotherapist in an CFS specialist team. The time it takes to return to the previous level of physical activity varies from person to person.


These usually last a few days and is a worsening of the symptoms beyond the normal day-to-day variation. Some flare-ups will develop into a relapse. For a flare-up:

  • It is useful to identify possible triggers, such as acute illness or overexertion, but there may be no clear trigger.

  • It is best to temporarily reduce activity levels, monitor symptoms and avoid returning to usual activity levels until the flare-up has resolved.


This is a more persistent and marked increase in symptoms, needing a substantial and sustained adjustment of energy management. For a relapse:

  • It is useful to identify possible causes.

  • It is best to reduce or stop some activities.

  • It is important to increase the frequency or duration of rest periods.

  • It is necessary to reassess energy limits to help stabilise the symptoms.

Ideally there should be a named contact in the CFS specialist team who can advise if the flare-up or relapse cannot be managed with planned self-management strategies.

How to help chronic fatigue syndrome

Rest and sleep

Rest periods in the daily routine are part of management strategies for all people with chronic fatigue syndrome.

Relaxation techniques at the beginning of each rest period can be helpful. It is important to balance the need for rest during the day against the need for sleep at night. Any changes to sleep pattern should be introduced gradually.

Physical functioning and mobility

Strategies to help maintain and prevent deterioration of physical function and mobility need to be carried out in small amounts spread out throughout the day.

Strategies should focus on joint mobility, muscle flexibility, balance, postural and positional support, muscle function, bone health and cardiovascular health.

Care and support plans in relation to physical functioning and mobility may include bed mobility, moving from lying to sitting to standing, transferring from bed to chair, using mobility aids, walking, joint mobility, muscle stretching, muscle strength, balance, and going up and down stairs.

People with CFS may experience intolerance of changing position, such as when first standing up. This may include postural orthostatic tachycardia syndrome (PoTS). A specialist referral may be needed if the symptoms are severe or worsening or if there are concerns that another condition may be the cause.

Dealing with pain

Chronic pain is commonly associated with CFS. Referral to specialist pain services may be needed.


People with chronic fatigue syndrome may be more intolerant of drug treatment. Therefore, medicines might need to be started at a lower dose than usual and then gradually increased.

Dietary management and strategies

Adequate fluid intake and a well-balanced diet are essential. A dietician with a special interest in CFS might be involved if someone is:

  • Losing weight and at risk of malnutrition.

  • Gaining weight.

  • Following a restrictive diet.

Children and young people with CFS who are losing weight, have poor growth or have a restricted diet should be assessed by a paediatric dietician with a special interest in CFS.

People with CFS may be at risk of vitamin D deficiency, especially those who are housebound or bed-bound.

There is not enough evidence to support routinely taking vitamin and mineral supplements as a cure for CFS or for managing symptoms.

Review of CFS in primary care

Adults with CFS should be seen for a review of their care and support plan in primary care at least once a year. Children and young people with CFS should have a review of their care and support plan at least every six months. These should be carried out or overseen by a paediatrician with expertise in CFS.

What is the outlook (prognosis)?

The long-term outlook for chronic fatigue syndrome varies from person to person. Although some people recover or have a long period of remission, many will need to adapt to living with CFS.

The outlook is better in children and young people than in adults. Chronic fatigue syndrome affects everyone differently and its impact varies widely.

For most people, symptoms still allow them to carry out some activities, whereas for others they cause severe impacts.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • Next review due: 19 Aug 2028
  • 21 Aug 2023 | Latest version

    Last updated by

    Dr Pippa Vincent, MRCGP

    Peer reviewed by

    Dr Surangi Mendis
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