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Fatigue is a condition in which a person becomes weary or exhausted. It is usually caused by overdoing some physical activity. It can also occur after a long period of mental stress. In some cases, it may occur for no clear reason.

What is going on in the body?

Most people have had fatigue at some point. The causes of fatigue range from working out or studying too hard to cancer. Sometimes no cause can be found.

What are the signs and symptoms of the condition?

A healthcare professional may want to know several things when a person complains of fatigue, such as:

• How long has the fatigue been present?
• Does it occur every day or only on some days?
• Is it getting worse, better, or staying the same?
• How many hours of sleep does the person get every night?
• How much stress is there in the person's life?
• How much activity or exercise does the person engage in?
• What kind of diet does the person follow?

The professional may also want to know about any fever, weight loss or pain. Questions about depression, menstrual periods in women and other symptoms may help in figuring out the cause of the fatigue. Hard bowel movements, dry skin and hair and always being cold could point to a low thyroid hormone in the blood.

What are the causes and risks of the condition?

Almost any sudden illness and many long-term illnesses can cause fatigue.

The more common causes of fatigue include:

• stress
• lack of sleep or difficulty sleeping
• infections, such as acute bronchitis, mononucleosis and AIDS
• anemia, a low red blood cell count
• working, studying or exercising too much
• lack of exercise or poor physical conditioning
• hormone imbalances, such as hypothyroidism
• hormonal changes in women during menopause
• chronic fatigue syndrome, in which a person has fatigue for long periods of time for no apparent reason
• depression or other psychological disorders, including emotional conflict, anxiety, frustration and boredom
• any of several autoimmune disorders, in which a person's immune system attacks his or her own body for no apparent reason
• toxin or chemical exposure, such as carbon monoxide or lead poisoning
• allergies
• medications, such as antihistamines, cancer chemotherapy, or certain medications used to treat depression and high blood pressure
• heart disease or disorders, including congestive heart failure
• lung diseases and disorders, including pulmonary edema and emphysema
• kidney disorders, including chronic renal failure
• liver disease, including cirrhosis
• digestive disorders
• uncontrolled diabetes
• cancer

There may be many other causes of fatigue as well. Sometimes a cause cannot be found.

What can be done to prevent the condition?

Prevention is related to the cause of the fatigue. For example, avoiding stress and overexertion, getting enough sleep, and eating a healthy diet can prevent many cases of fatigue.

How is the condition diagnosed?

Sometimes, the cause of the fatigue is clear to the healthcare professional after a thorough history and physical exam. In other cases, further tests may be needed, depending on what is suspected. The complete blood count (CBC) is the most common of these, because it can confirm anemia, one of the most frequent causes of fatigue. Sometimes an extended workup stretched over several visits is needed. A chest X-ray is helpful if lung disease is suspected.

What are the long-term effects of the condition?

Fatigue can seriously limit a person's ability to work, go to school, and maintain relationships. Severely affected people may need to rest for most of the day. People with chronic fatigue syndrome often become frustrated because of the lack of effective treatment for this condition. Other long-term effects depend on the underlying condition.

What are the risks to others?

Fatigue itself is not contagious and poses no risk to others. However, fatigue may sometimes be caused by infections that are contagious.

What are the treatments for the condition?

Specific treatment for fatigue is directed at the cause. For example, a person may need antibiotics to treat an infection or thyroid medication to treat low thyroid levels. Those with depression often need drugs to treat their condition. Those with cancer may need surgery, chemotherapy, or radiation therapy. Regular exercise without overexertion, getting enough sleep, eating a healthy diet, and decreasing stress levels can often help.

What are the side effects of the treatments?

Side effects depend on the treatments used. All medications have possible side effects. These may include allergic reactions, stomach upset, and headache. Surgery can be complicated by bleeding, infection, or an allergic reaction to the anesthetic.

What happens after treatment for the condition?

What happens after treatment depends on the cause of fatigue. If the fatigue goes away, a person may not need further treatment. Those who were overexerting may need no further treatment once they get some rest. Those with diabetes generally need further treatment and monitoring even if their fatigue goes away.

How is the condition monitored?

A person can monitor his or her own energy level and fatigue at home. Any changes in these levels can be reported to the healthcare professional. The underlying cause of fatigue may or may not need further monitoring.