Body aches and fatigue are symptoms of both fibromyalgia and chronic fatigue syndrome, but research shows primary symptoms and pathophysiology set these conditions apart.

Fibromyalgia is a condition featuring persistent musculoskeletal pain throughout the body. In addition to chronic pain, extreme fatigue in the absence of exertion is also a common symptom.

Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), is a condition of overwhelming fatigue that can be accompanied by physical aches and pains.

With how similar these two conditions appear on the surface, it can be challenging to know which one is affecting you — or if you’re experiencing both.

Literature acknowledges a significant overlap in the symptoms of fibromyalgia and chronic fatigue syndrome (CFS) — so much so that experts have continued to debate whether or not these are two separate conditions or one and the same.

A 2020 research commentary points out there are biochemical, genetic, and physiological differences between fibromyalgia and CFS that support them being separate conditions.

Both, however, remain medically unexplained illnesses predominantly affecting biological women, and a link between them can’t be completely ruled out yet.

Symptomatically, the main difference between fibromyalgia and CFS has to do with the prevalence and presentation of fatigue and muscle pain.

In fibromyalgia, musculoskeletal pain and tenderness are the dominant features. Extreme fatigue is secondary but still common.

In contrast, fatigue is the main symptom of chronic fatigue syndrome. It often worsens with exertion, and the start of symptoms can usually be traced to an abrupt flu-like illness. Body pain and tenderness are common but don’t occur in all chronic fatigue cases.

Apart from symptoms, pathophysiological processes also clearly define these conditions, according to the 2019 commentary.

Chronic fatigue syndrome and fibromyalgia have major pathological differences in areas of:

  • sleep pathology
  • spinal fluid composition
  • hormone release
  • exercise response
  • neurotransmitter activity
  • comorbid mental disorders

Fibromyalgia symptoms

Classic symptoms of fibromyalgia include:

  • widespread musculoskeletal pain and touch tenderness
  • fatigue, particularly when waking, during the mid-afternoon, and after periods of inactivity
  • difficulty concentrating (often known as “fibro fog”)
  • depression
  • anxiety
  • headaches
  • numbness or tingling in the extremities
  • gastrointestinal distress
  • dry eyes
  • breathlessness
  • difficulty swallowing
  • irregular heartbeat
  • sleep disturbances
  • sensory sensitivity

Chronic fatigue syndrome symptoms

Class symptoms of chronic fatigue syndrome include:

There are no tests that can definitively diagnose fibromyalgia or chronic fatigue syndrome.

You receive a diagnosis based on the presentation of your symptoms and if no other conditions can account for what you’re experiencing.

Ruling out other causes can be a process on its own. You may need a battery of tests, including:

  • blood work
  • diagnostic imaging
  • urine tests
  • psychological evaluations
  • neurological tests
  • sleep studies

When the diagnosis points to fibromyalgia or chronic fatigue syndrome, doctors turn to the clinical criteria outlined for these conditions.

A diagnosis of fibromyalgia comes after meeting the American College of Rheumatology’s criteria of:

  • Widespread pain index (WPI) of at least 7, with symptom severity rated as 5; or WPI between 3 and 6, with symptom severity of at least 9.
  • Symptoms have been present for at least 3 months.
  • No other disorder accounts for symptoms.

You may receive a chronic fatigue syndrome diagnosis if you meet the latest diagnostic criteria from the National Academy of Medicine, which includes:

  • presence of symptoms for more than 6 months
  • symptoms are moderate to severe for at least 50% of the time
  • presence of functional impairment accompanied by new-onset fatigue unrelated to exertion and not relieved by rest
  • post-exertional malaise
  • unrefreshing sleep
  • presence of cognitive impairment and/or orthostatic intolerance

It’s possible to have both fibromyalgia and chronic fatigue syndrome. Studies show as many as 34% of people diagnosed with chronic fatigue syndrome also live with fibromyalgia.

There’s no cure for fibromyalgia or chronic fatigue syndrome, and no standardized treatment protocol that works for everyone.

Because the underlying causes of these conditions are unknown, treatment typically requires a multidisciplinary approach with professionals like neurologists, psychologists, physical therapists, and sleep specialists.

Both conditions may involve the use of:

If you’re living with fibromyalgia, you may also benefit from neuromodulation procedures like transcranial stimulation.

Chronic fatigue syndrome treatments may include corticosteroid therapy, antiviral therapy, immunotherapy, and microbiome-targeted treatments like fecal microbiota transplant.

Fibromyalgia and chronic fatigue syndrome are very similar conditions featuring body aches and persistent fatigue.

In fibromyalgia, however, widespread body pain and tenderness are the dominant symptoms. In chronic fatigue syndrome, fatigue is the dominant symptom.

It’s possible to live with both of these conditions simultaneously. Due to their close symptomology and unknown causes, available treatments also overlap.