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What Causes Extreme Fatigue?

author image Dr. Tina M. St. John
Tina M. St. John runs a health communications and consulting firm. She is also an author and editor, and was formerly a senior medical officer with the U.S. Centers for Disease Control and Prevention. St. John holds an M.D. from Emory University School of Medicine.
What Causes Extreme Fatigue?
Bedrest characteristically fails to relieve fatigue. Photo Credit Jupiterimages/Goodshoot/Getty Images

People with extreme fatigue experience profound tiredness and lack of energy that persist despite adequate rest and sleep. Because the body requires oxygen to generate energy, diseases and conditions that disrupt the delivery of oxygen to the body tissues often cause severe fatigue. Diagnosis of the underlying cause of extreme fatigue facilitates the development of a treatment plan to help diminish this frequently debilitating symptom.


Anemia is a common condition characterized by an abnormally low number of red blood cells circulating in the bloodstream. Anemia frequently causes fatigue, according to the National Heart Lung and Blood Institute. The level of fatigue increases in proportion to the severity of the anemia. Among people with a markedly low red blood cell count, fatigue is often extreme. Long-standing anemia can hurt heart function, further aggravating fatigue.

Many genetic and acquired diseases and conditions can cause anemia. These include iron deficiency, chronic kidney disease, pernicious anemia, sickle cell disease and leukemia. Disorders that cause acute or chronic blood loss can also cause profound anemia, including peptic ulcer disease, Crohn's disease and bleeding associated with liver failure.

Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease, or COPD, is a progressive lung condition caused by long-standing inflammation that damages the airways and air sacs. COPD-associated damage limits the capacity of the lungs to transfer oxygen from inhaled air to the bloodstream, leading to insufficient oxygen in the body tissues. Chronic oxygen deprivation leads to persistent fatigue, a common symptom of COPD. As COPD progresses, the level of fatigue increases.

As of 2009, the Centers for Disease Control and Prevention estimated that as many as 24 million Americans have COPD. Most cases of COPD are attributable to cigarette smoking.

Heart Failure

Heart failure describes the condition in which diminished heart function leads to insufficient oxygen-rich blood delivery to body tissues, resulting in chronic fatigue. The level of fatigue associated with heart failure increases as heart function decreases. Among people with advanced heart failure, fatigue typically proves severe.

Different types of heart disease can lead to heart failure. Thee include coronary artery disease, heart attack, hypertensive heart disease and cardiomyopathy.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disorder characterized by activity-limiting fatigue of at least six months that isn't attributable to another medical cause, says the National Library of Medicine online encyclopedia MedlinePlus. A wide variety of other symptoms may accompany chronic fatigue syndrome, including headaches, body aches, weakness, sore throat, irritability, poor concentration and forgetfulness. Depression and other mental health problems also commonly occur among people with chronic fatigue syndrome.

The American College of Physicians reports that an estimated 500,000 Americans have chronic fatigue syndrome, which most commonly affects women age 25 through 45. The cause of chronic fatigue syndrome remains an area of active biomedical research.

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