Chronic fatigue syndrome, also known as myalgic encephalomyelitis or ME/CFS, is a complicated disorder.

It causes extreme fatigue that lasts for at least six months. Symptoms worsen with physical or mental activity but don't fully improve with rest.

The cause of chronic fatigue syndrome is unknown, although there are many theories. Experts believe it might be triggered by a combination of factors.

There's no single test to confirm a diagnosis of chronic fatigue syndrome. You may need a variety of medical tests to rule out other health problems that have similar symptoms. Treatment for the condition focuses on easing symptoms.


Symptoms of chronic fatigue syndrome can vary from person to person, and the severity of symptoms can fluctuate from day to day. In addition to fatigue, symptoms may include:

  • Extreme exhaustion after physical or mental exercise.
  • Problems with memory or thinking skills.
  • Dizziness that worsens with moving from lying down or sitting to standing.
  • Muscle or joint pain.
  • Unrefreshing sleep.

Some people with chronic fatigue syndrome have headaches, sore throats, and tender lymph nodes in the neck or armpits. People with the condition also may become extra sensitive to light, sound, smells, food and medicines.

When to see a doctor

Fatigue can be a symptom of many illnesses. In general, see your doctor if you have persistent or excessive fatigue.


The cause of chronic fatigue syndrome is still unknown. A combination of factors may be involved, including:

  • Genetics. Chronic fatigue syndrome appears to run in some families, so some people may be born with a higher likelihood of developing the disorder.
  • Infections. Some people develop chronic fatigue syndrome symptoms after getting better from a viral or bacterial infection.
  • Physical or emotional trauma. Some people report that they experienced an injury, surgery or significant emotional stress shortly before their symptoms began.
  • Problems with energy usage. Some people with chronic fatigue syndrome have problems converting the body's fuel, primarily fats and sugars, into energy.

Risk factors

Factors that may increase your risk of chronic fatigue syndrome include:

  • Age. Chronic fatigue syndrome can occur at any age, but it most commonly affects young to middle-aged adults.
  • Sex. Women are diagnosed with chronic fatigue syndrome much more often than men, but it may be that women are simply more likely to report their symptoms to a doctor.
  • Other medical problems. People who have a history of other complex medical problems, such as fibromyalgia or postural orthostatic tachycardia syndrome, may be more likely to develop chronic fatigue syndrome.


Symptoms of chronic fatigue syndrome can come and go, and often are triggered by physical activity or emotional stress. This can make it difficult for people to maintain a regular work schedule or to even take care of themselves at home.

Many people may be too weak to get out of bed at different points during their illness. Some may need to use a wheelchair.