Related Conditions

Some symptoms of ME/CFS warrant a separate diagnosis of their own.
Some conditions commonly occur alongside ME/CFS.

Orthostatic intolerance

Orthostatic intolerance (OI), an aspect of autonomic nervous system dysfunction, is the inability to function when standing or sitting up, which is relieved only by lying down. For someone who is severely ill, an incline of only 20% has been shown to induce symtoms of OI.

OI comes in many forms. The two most commonly identified in ME/CFS are:

  • postural orthostatic tachycardia syndrome (POTS)
  • neurally mediated hypotension (NMH)

Other autonomic dysfunctions

Additional autonomic nervous system dysfunctions that may warrant a specific diagnosis include:

  • Raynaud's
  • dysphagia (difficulty swallowing)
  • migraine


Fibromyalgia (FM) is a common, chronic condition marked by widespread pain, accompanied by extreme fatigue, sleep disturbance and cognitive problems.

Many people with ME/CFS have diagnosable Fibromyalgia.

Multiple Chemical Sensitivity

Multiple Chemical Sensitivity (MCS) is the occurrence of symptoms in response to the presence of low levels of chemicals, such as volatile organic compounds (VOC) and organophosphates. Common sources include fragrances, cleaning products and paints.

Some people have MCS before the illness and ME/CFS makes them worse. For others, MCS is experienced for the first time when they become ill with ME/CFS.

Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) is characterised by abdominal pain and bloating, with constipation and/or diarrhoea. It may be accompanied by nausea and other gut symptoms.

Gynaecological conditions

Women with ME/CFS tend to have higher than usual rates of gynaecological disorders. Examples include: early menopause, endometriosis, menstrual abnormalities.

Viral and bacterial infections

There are some viral and bacterial infections that appear to be common precursors of ME/CFS. For example: Epstein-Barr Virus and other herpesviruses, Lyme disease, Ross River virus, Q fever, mycoplasma pneumonia. Identification and treatment of comorbid infections may reduce the severity of ME/CFS symptoms.

Post-viral fatigue and post-viral fatigue syndrome

Post-viral fatigue (PVF) is a common and usually self-limiting symptom following an acute viral infection.

Post-viral fatigue syndrome (PVFS) is PVF accompanied by a symptom complex, in addition to the fatigue.

If the syndrome persists and becomes debilitating, then an ME/CFS diagnosis should be considered. In particular, the presence of post-exertional malaise (PEM) will indicate ME/CFS.

This includes people who have been infected by the COVID-19 virus.

Last edited: 28 April, 2023