Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

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This clinical tool supports primary care clinicians in recognizing, assessing, diagnosing and managing Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). ME/CFS is a chronic complex medical condition that impacts multiple organ systems and is not a psychological condition. The symptoms of ME/CFS can be severe, significantly affecting quality of life. The medical system has dismissed many patients living with ME/CFS resulting in patients not receiving the care they need. While there is no cure, reduced symptom severity and improved quality of life may be achieved through accurate diagnosis, detailed assessment and targeted management. Many individuals with post COVID-19 condition can also meet ME/CFS criteria. It is critical that primary care clinicians be comfortable with the diagnosis and management of the condition. 

Clinical presentation and diagnosis

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ME/CFS is a chronic life-altering condition, ranging from mild to very severe – resulting in a wide range of functional impairments, where some patients can work while others are homebound or bedbound. ME/CFS affects many different organ systems, and the constellation of symptoms can vary between individuals and can fluctuate from day to day. See examples of clinical manifestations (page 2-3).1,2

Diagnostic criteria1-3

Diagnosis of ME/CFS is clinical, owing to the absence of biomarkers, and based on detailed clinical history and physical examination.  

  • Suspect ME/CFS if symptoms are present for six weeks or more (Approaching a management plan). 
  • Confirm ME/CFS if core symptoms are present for six months for more. 

Diagnosis requires that the patient have the following three symptoms in addition to one of the other two:

The above diagram displays core symptoms at a high-level, see detailed descriptions below.

Core symptoms

A substantial reduction or impairment in the ability to engage in pre-illness levels of activity (occupational, educational, social, or personal life) that:3

  • Lasts for more than 6 months.
  • Is accompanied by fatigue that is:
    • Often profound.
    • Of new onset (not life-long).
    • Not the result of ongoing or unusual excessive exertion.
    • Not substantially alleviated by rest.
  • Is a central symptom of ME/CFS.6
  • Following physical, mental, or emotional exertion that would not have posed an issue pre-illness, the patient experiences increased fatigue and other symptoms.3
  • PEM may last days, weeks, months or longer. Worsening of PEM symptoms that lasts a few days, beyond the patient’s day to day variation is often referred to as a crash or flareup. A sustained exacerbation of PEM symptoms beyond this, resulting in a need to substantially adjust energy management, is often referred to as a relapse.2 
  • PEM may have immediate or delayed onset. Symptoms typically worsen a few hours to 72 hours after activity or exposure.4
  • For more information on how to identify Post-exertional Malaise see INESSS Support for People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) (page 2). 
  • Even without specific sleep changes, patients may not feel rested or have fatigue alleviated after a full night of sleep.3 
  • May also include sleep disturbances (insomnia, daytime sleepiness, irregular sleep cycles, restless leg syndrome, sleep apnea).5,6 
  • Difficulties with cognition, memory, executive function, and information processing, alongside attention deficit and impeded psychomotor functions. Patients frequently describe experiencing brain fog.3
  • Can worsen due to exertion, effort, prolonged standing, stress, or time constraints, and could significantly affect a patient’s capacity to sustain full time employment or education.3

Symptoms related to orthostatic intolerance, such as dizziness, fainting, heightened fatigue, cognitive difficulties, headaches, or nausea, are aggravated when maintaining an upright posture (either standing or sitting) in daily activities, and improve (though not always completely) when lying down.3  See CEP’s POTS tool for screening and diagnosis of POTS.  

Other commonly co-occuring symptoms include:2

  • Temperature hypersensitivity resulting in profuse sweating, chills, hot flushes, or feeling very cold
  • Neuromuscular symptoms, including twitching and myoclonic jerks
  • Flu-like symptoms, including sore throat, tender glands, nausea, chills or muscle aches
  • Intolerance to certain foods, alcohol and chemicals
  • Heightened sensory sensitivities, including light, noise, touch and smell, or visual disturbances
  • Pain, including touch, myalgia, headaches, eye pain, abdominal pain or joint pain without acute redness, swelling or effusion
  • Sicca symptoms: dry eyes and dry mouth
  • Gastrointestinal symptoms  
  • Genitourinary symptoms 
  • Respiratory symptoms, such as air hunger 


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Carry out a comprehensive assessment to determine differential diagnoses, confirm a diagnosis and address comorbid conditions. Assessments can be conducted over a series of appointments. 

Assessments should include:2,5

    • A ME/CFS assessment
    • Family history of ME/CFS
    • Medication history
    • Daily routines, including sleep-wake patterns and overall functioning
    • Level of severity and impact of the symptoms on the patient’s ability to function (Activities of Daily Living (ADLs), Instrumental Activities of Daily Living (iADLs), ability to work, engage in social activities)
    • Impact of the condition on the patient’s personal well-being e.g., ask about coping strategies, screen for mental health symptoms, ask about current supports
    • Investigations to identify other diagnoses/causes of symptoms or comorbidities Differential diagnosis and comorbid conditions

Diagnostic code
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Practice points:2

  • Due to severe physical fatigue and cognitive difficulties, some patients may not be able to physically visit the office or may have difficulty explaining their symptoms at certain times. 
  •  If a patient can visit the office, clinicians might not be witnessing the full severity of post-exertional malaise (PEM) or other symptoms at that point in time.  
  • Ask about changes to the frequency and severity of symptoms over the past several months. 
  • Be aware of the fluctuating nature of ME/CFS and how this can mean that people can present differently throughout their illness. 


Understanding the severity of a patient’s condition can help with identifying their individual needs and appropriate management strategies. The following descriptions offer insight into how symptoms affect daily functioning:2

Validated or recognized clinical tools to assess symptom severity and impact include:6-8

Can be assessed using prolonged orthostatic testing for example:

  • Passive stand test such as the NASA Lean Test. Consider referring to the Clinician Resources for test instructions. 
Explaining the diagnosis and prognosis to patients
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Differential diagnosis and comorbid conditions

There is currently no diagnostic test for ME/CFS. Use clinical judgment when deciding to pursue additional investigations to identify other diagnoses or comorbidities. Investigations should be tailored as much as possible to suit the energy capacity of the patient as some investigations could trigger post-exertional malaise, for example, allowing breaks or spreading assessments over several days.2,5,6 INESSS provides examples of relevant tests (page 7). Comorbidities contribute considerably to the severity of the clinical manifestations of ME/CFS, hence the importance of stabilizing them.5 For examples of differential diagnoses or possible comorbid conditions, see NICE’s examples of differential diagnoses and comorbid conditions (page 57) or INESSS’ differential diagnoses and comorbidities table (page 5).   


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When approaching a management plan:2,5,6

Practice point: Implement management strategies to help patients manage their symptoms even when ME/CFS is suspected but not yet confirmed at the 6-month mark.

Management of comorbidites: Ensure that management strategies for comorbidities are also appropriate for ME/CFS patients. For example, some exercise rehabilitation protocols for POTS or Fibromyalgia do not consider PEM and/or coexisting ME/CFS. For patients with POTS or Fibromyalgia with comorbid ME/CFS, pacing takes priority over exercise to stabilize energy and avoid PEM.2

Considerations for patients with severe or very severe ME/CFS

There are additional factors to consider when caring for patients with severe or very severe ME/CFS (Severity). Patients in this category may:2

  • Need a low-stimulus environment to restrict exposure to factors that may cause PEM. 
  • Be housebound or bedbound and need support with all activities of daily living. 
  • Have sensitivity to touch and need careful physical contact when supported with activities of daily living. 
  • Be unable to communicate without support and may choose an advocate to support them in communication.  
  • Be unable to eat and digest food easily and require support with hydration and nutrition. 
  • Encounter barriers to information access due to difficulty with screens, sound and light sensitivity, headaches affecting their ability to read, or brain fog affecting their concentration. 

Clinical accommodation and disability support

Beyond the non-pharmacological and pharmacological management strategies outlined below, patients whose symptoms significantly affect their ability to work may require accommodation during appointments and supplementary disability income support. Many patients with ME/CFS will need some form of disability support and will need their clinician’s assistance in obtaining it. The presentation of symptoms can look different from patient to patient and can present on different timelines. It is important to keep this in mind during assessment and when providing corresponding documentation for disability claims. 

Streamlining appointments for enhanced patient convenience and productivity4,6

  • Encourage patients to write down their history, including medications they are taking, before coming to the appointment to mitigate cognitive difficulty and fatigue during the appointment. 
  • Inform patients that they can bring a friend or family member to take notes, which they can review later. 
  • Provide recommendations to patients in writing so they are easier to remember. 
  • Schedule follow-up visits at regular intervals that also work for the patient with the ability to adjust as needed. 
  • Encourage patients to write out the following updates before follow-up visits: 
    • Changes in condition from their last visit, including anything that has helped since their last visit. 
    • Most troublesome symptoms.  
    • All medications and supplements with corresponding doses.  
  • Tailor investigations to suit patients’ energy capacity to avoid post-exertional malaise (e.g., allowing breaks, informing patients about at-home testing options with associated fees for certain labs). 
  • Consider flexible appointment options to accommodate patients’ energy management needs (e.g., phone or virtual appointments and in-home services where feasible). 
  • Consider arranging appointments to reduce wait times and schedule them at times when the patient’s energy levels are typically higher. 
  • Limit the presence of sensory stimuli during appointments (e.g., dimming lights, speaking in low voices, setting the room to a comfortable temperature). 
  • Offer patients the option to lie down on the exam table during the appointment if needed. 

Non-pharmacological management2,4,5

Non-pharmacological strategies can be used to manage common symptoms of ME/CFS and improve quality of life. They can be implemented in patients where ME/CFS is suspected and not yet confirmed as well as those with a confirmed diagnosis. 

Non-pharmacological strategies

Practice point: Activity pacing and energy management are crucial strategies for ME/CFS symptom management. Share guidance on pacing and energy levels with patients. Discuss the principles, benefits, and risks of energy management.2


Explain that this strategy:2

  • Is not curative. 
  • Involves patient-led self-management with guidance from a healthcare professional. 
  • Includes pacing for all types of activity (cognitive, physical, emotional and social) and considers the overall level of activity. 
  • Helps patients with managing their energy expenditure to reduce the risk of exceeding their limits and triggering post-exertional malaise (PEM) or worsening their symptoms. 
  • Adopts a flexible, tailored approach where activity is adjusted or maintained according to the patient’s needs (upwards after a period of stability or downwards when symptoms are worse). 
  • Requires a long-term commitment − reaching stabilization or increasing activity can take weeks, months or sometimes years. 

Educate patients on the types of activity that may trigger PEM so they can develop an energy management plan that includes pacing for all relevant types of activity and learn when to incorporate rest or other energy restoring measures. The plan should be developed around the patient’s priorities and goals as well as realistic expectations.2

Work with patients to establish an individual activity pattern within their current energy limits that minimizes their symptoms. For example:2

  • Help patients identify their activity threshold as the initial step, which may involve reducing activity.
  • Plan periods of rest and activity and incorporate the need for pre-emptive rest.
  • Alternate and vary between types of activity and break activities into small chunks.

For patients with ME/CFS who have stabilized and are able to engage in some physical activity without triggering PEM, the approach should consider:6

  • Each patient’s starting point/baseline level of function.
  • The amount of activity they are currently able to do without symptom exacerbation.
  • Evaluation of their response to the exertion if engaging in physical activity.

These patients should begin activities at a very low intensity and increase slowly in small increments only if symptoms of PEM are not exacerbated. Ideally, the patient should obtain support from allied healthcare providers, such as athletic therapists, etc., who have experience working with ME/CFS patients.6

Practice point: Graded Exercise Therapy is NOT recommended for patients with ME/CFS as it may trigger post-exertional malaise (PEM). Avoiding PEM should be prioritized over standard physical activity recommendations that may be suggested for comorbid conditions. When considering the role of any physical activity in a patient’s care, respect the patient’s energy capacity.2,5

Some potential sources of energy expenditure, include:4

  • Other acute illnesses (e. g., cold or flu)  
  • Non-stabilized comorbidities 
  • Environmental factors (e.g., proximity of allergens, change of temperature or season changeover). 
  • Performing activities that require effort:
    • Physical: brushing teeth, dressing, showering, climbing stairs, doing laundry, etc. 
    • Cognitive: listening to music, watching television, reading, writing, etc.
    • Emotional: interactions with others, bereavements (e.g., difficulty returning to previous activities), stressful events (e.g., insurance claims, arguments, or illness of a loved one), happy events (e.g., holiday, birth), etc. 
  • Sensory stimuli (e.g., sound, light, touch) 
  • In patients with autonomic-like clinical manifestations: 
    • Postprandial state 
    • Upright position (sitting or standing) – worse if stationary

Factors that can facilitate energy gain, include:4

  • Food intake  
  • Rest  
  • Sleep 
  • Autonomic nervous system regulation strategies (e.g., lying down) if dysautonomic-like clinical manifestations are present. 

Educate ME/CFS patients about the role of rest in ME/CFS management and help them develop an individualized sleep/rest management plan that considers: 

  • Introducing rest periods into their daily routine while considering nocturnal sleep patterns. 
  • Adding relaxation techniques at the beginning of each rest period, if helpful. 
  • Developing good sleep habits and introducing changes to sleep patterns gradually, 
  • Eye masks, ear plugs, light therapy and screen filters.  
  • A sleep medicine referral based on reported symptoms.  
  • Services offering OHIP-funded CBT for insomnia. 

  • Includes Postural Orthostatic Tachycardia Syndrome (POTS). See CEP’s POTS tool for strategies to manage Orthostatic Intolerance and related symptoms.
  • Exercise or physical activity strategies should be approached with caution as they can trigger PEM in ME/CFS patients. Prioritizing the avoidance of PEM should take precedence over managing other symptoms.  

  • Some strategies for dealing with pain (especially in those with comorbid Fibromyalgia) can be found in CEP’s Fibromyalgia tool.
  • Strategies for managing pain or comorbidities should respect the patient’s energy capacity to avoid triggering PEM. For example, use caution when considering physical activity as a management strategy. 
  • Emphasize the importance of adequate fluid intake and a balanced diet. 
  • Strategize with patients and/or their caregivers to minimize difficulties caused by food and nutrition, including gastrointestinal symptoms, changes to appetite, difficulty swallowing, sore throat or barriers to buying, preparing and eating food. 
  • Urge patients experiencing nausea to maintain adequate fluid intake and suggest consuming small, regular meals, as avoiding food and drink could exacerbate their nausea. 
  • Recognize the risk of vitamin D deficiency, especially among housebound or bedbound patients. Those on acid-controlling medications for GERD may also be deficient in vitamin B12 and magnesium. As needed, discuss the role of supplements in ME/CFS management. There is insufficient evidence to support routinely taking vitamin and mineral supplements as a cure for ME/CFS or to manage symptoms. Patients with ME/CFS may have increased sensitivity to natural health products. Discuss safe practices related to taking natural health products if a patient chooses to incorporate them into their routine. 
  • Cognitive behavioural therapy (CBT) or other support interventions can help patients cope with having a chronic illness. Refer patients as appropriate. 
  • Education for patients and their caregivers about ME/CFS can enhance understanding of the condition and help caregivers offer useful assistance and support. Consider referring to the Patient and Caregiver Resources for educational materials suggested by persons with lived experience 
  • Referrals to occupational therapy and social workers can offer support in adapting Activities of Daily Living and accessing supports such as home care services and government disability programs. 
  • Pacing is a priority for those experiencing more severe symptoms to stabilize energy and avoid PEM.  

Pharmacological management

There is limited evidence regarding pharmacological treatments for ME/CFS. There is currently no pharmacological cure for the condition. Some patients with ME/CFS have found the use of pharmacological interventions to be helpful in managing symptoms, including low-dose and off-label medications, under the guidance of healthcare professionals. The use of medications for symptom management can be discussed with patients using clinical judgement to adapt best practices to the individual. Consideration should be given to managing identified comorbidities.2

Practice point: When considering pharmacological management options, recognize that ME/CFS patients may be less tolerant of medication. Be sure to start low and go slow. Where feasible, consider medications that target multiple clinical symptoms to minimize adverse effects and polypharmacy.2,5

For guidance on pharmacological management of symptoms overlapping with other conditions such as: