CFS Meaning: Here’s What It Means and How to Use It

Do you know what CFS means? Not to worry; we’ll tell you. Read on to discover the meaning of CFS, how it’s used, and more.

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Whether from a long night spent cramming for a test, an all-nighter playing video games, an overactive mind, or a lumpy-bumpy mattress that makes sleep seemingly impossible, everyone feels a little fatigued from time to time. Some people, however, feel fatigued a lot of the time — regardless of getting a good night’s rest. 

A disorder characterized by extreme tiredness, chronic fatigue syndrome (CFS) effects the lives of up to 2.5 million Americans, according to the Centers for Disease Control and Prevention (CDC). 

Interested in learning more? We can help. Read on to discover our complete guide on CFS.

What Is the Definition of CFS?

CFS is the abbreviation for a complex illness known as chronic fatigue syndrome. This syndrome also has a few other names: Systemic Exertion Intolerance (SEID), Myalgic Encephalomyelitis (ME), and ME/CFS.

Those diagnosed with CFS are often noted to have overwhelming fatigue that is not improved by rest and oftentimes can confine the person to bed. 

What Are the Symptoms of CFS?

Post-exertional malaise (PEM) is commonly agreed to be the worst symptom of CFS. Some of the other symptoms include:

  • Problems with concentration or memory; usually resulting in “brain fog,” which is a term used to define the symptom of slowed or confused thinking
  • Physical activity now results in acute tiredness
  • Frequent sore throat; usually associated with a flu-like feeling, dizziness, and headaches
  • Sleep problems, such as non-restorative sleep
  • Enlarged and/or tender lymph nodes in your armpits or neck
  • Unexplainable joint and/or muscle pain 
  • Mental exercise that results in severe fatigue

As we discussed before, post-exertional malaise is arguably one of the worst symptoms of chronic fatigue syndrome. PEM is defined as the worsening of any (more commonly all) symptoms following even the smallest of amounts of physical activity or mental activity.

One of the other commonly seen symptoms in those affected by CFS would be the inability to perform daily tasks — even if they were once able to do this task with ease. Some of these tasks may include preparing your favorite meal or even bathing yourself. 

It should be noted to the reader that this illness is more often than not a misunderstood syndrome, even at times misunderstood by healthcare providers. 

How Is CFS Diagnosed?

Chronic fatigue syndrome can affect anyone — this includes even children. It has over time proven to be more common in women but develops in everyone, most commonly in their mid-40s and mid-20s.

Even though the illness can affect the masses, there is no specific test to date that can serve as a stand-alone test for CFS. Because there is no specific test for ME/CFS, it is an illness that many healthcare providers have difficulty understanding. 

One of the only ways a healthcare provider can diagnose a person with ME/CFS is to go through each patient’s symptoms, ruling out every condition one by one, as CFS shares the same symptoms with many known illnesses.

As the patient and healthcare provider work together over time, if the symptoms in question do not get better as quickly as the healthcare provider deems appropriate, the patient is often diagnosed with CFS.

While CFS was once an almost controversial diagnosis, we have progressed in modern science over time. As such, ME/CFS is now a more widely accepted illness in the medical community.

What Body Systems Can CFS Affect?

Since Myalgic Encephalomyelitis or the more commonly used ME/CFS is not just a chronic disease but a debilitating one, it can affect multiple body systems. 

This often can impact the brain and other systems of the body, including but not limited toL the immune system, the body’s energy production, and even the nervous system. 

In Conclusion

By now, we hope it’s clear that CFS can be defined as “chronic fatigue syndrome.” That said, it is not a disorder to be taken lightly. Myalgic encephalomyelitis is an extremely disabling and complicated disorder characterized by acute fatigue.


  1. Definition of CFS | NCI Dictionary of Cancer Terms 
  2. Chronic fatigue syndrome (CFS) | Better Health Channel
  3. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) | CDC
  4. Myalgic Encephalomyelitis (“Chronic Fatigue Syndrome”) | Health