What Are the Causes of Unexplained Fatigue?

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  • Written By: Alex Tree
  • Edited By: Melissa Wiley
  • Last Modified Date: 14 June 2019
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Chronic fatigue syndrome, sleep apnea, and depression are some possible causes of unexplained fatigue. In addition, a deficiency in vitamins can be to blame. Fatigue syndromes and depression can be difficult to diagnose based on unexplained fatigue alone. Sleep apnea is typically diagnosed after having the patient perform a sleep study, where his or her sleep is monitored throughout the night. Sometimes due to an eating disorder, obesity, or poor diet, a person develops a vitamin deficiency with symptoms like unexplained fatigue.

Unexplained fatigue is sometimes caused by chronic fatigue syndrome, a health condition resulting in long-term fatigue. The problem must be ongoing for at least six months, not fixable with rest, and other potential health conditions should be ruled out for a diagnosis to be made. Treatment is often a form of behavioral therapy, but many people with this condition do not completely recover. Some doctors do not believe chronic fatigue syndrome exists and put off an official diagnosis in favor of searching for other causes of the patient’s unexplained fatigue.


Sleep apnea is a sleep disorder that causes people to stop breathing or breathe poorly while asleep. People suffering from sleep apnea might wake up dozens of times during the night to catch their breath, but not realize this because they are not fully awake. This disorder often goes undiagnosed, especially in minor cases, but it can be fatal in severe cases. Some warning signs of sleep apnea are unexplained fatigue, chronic snoring, and gasping for breath while trying to sleep. More treatments are available for sufferers of sleep apnea than chronic fatigue syndrome, and a patient can even be rid of his or her symptoms after a few months.

Fatigue and depression are related, and having one problem can lead to having the other. While it is understandable that someone with unexplained fatigue becomes depressed, some researchers are curious about how depression leads to fatigue. They are still studying the two conditions, but it seems that depressed people may become listless and stop participating in physical activities. Physical activities appear to protect against depression.

Many vitamin deficiencies can cause fatigue, such as a deficiency in vitamins E, D, and B. These deficiencies usually have other symptoms, like loss of smell, bad breath, and diminished reflex responses. A doctor can help diagnose and treat a vitamin deficiency. These health problems that potentially cause unexplained fatigue are some of the easiest to detect and treat.



Discuss this Article

Post 3

@ZipLine-- Have you been tested for arthritis, Lyme disease and viral infections?

These can all cause unexplained, chronic fatigue symptoms.

It's also possible to have fatigue due to psychological reasons even though there is nothing physically wrong. I think this is called "psycho-symptomatic."

Post 2

@ZipLine-- It might be fibromyalgia or chronic fatigue syndrome. But if you have either, good luck getting a diagnosis. Both of these are very difficult to diagnose because no medical testing can confirm it. When doctors run out of possibilities, it is usually labeled chronic fatigue syndrome and the treatment is pain relievers.

I know exactly what you're feeling. I've been suffering from depression and unexplained fatigue for years. Even though I have the diagnosis of chronic fatigue syndrome now, I still don't know why I have it.

Post 1

I've had unexplained fatigue and exhaustion for the past year and a half. I've been to three different doctors and have had numerous diagnostic testing. Everything always comes back normal. I'm at my wit's end and so are my doctors. What is wrong with me?!

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