Fatigue is a feeling of weariness, tiredness, or lack of energy.

Fatigue is different from drowsiness. In general, drowsiness is feeling the need to sleep, while fatigue is a lack of energy and motivation. Drowsiness and apathy (a feeling of indifference or not caring about what happens) can be symptoms of fatigue.

Fatigue can be a normal and important response to physical exertion, emotional stress, boredom, or lack of sleep. However, it can also be a nonspecific sign of a more serious psychological or physical disorder. When fatigue is not relieved by enough sleep, good nutrition, or a low-stress environment, it should be evaluated by your doctor. Because fatigue is a common complaint, sometimes a potentially serious cause may be overlooked.

The pattern of fatigue may help your doctor determine its underlying cause. For example, if you wake up in the morning rested but rapidly develop fatigue with activity, you may have an ongoing physical condition like an underactive thyroid. On the other hand, if you wake up with a low level of energy and have fatigue that lasts throughout the day, you may be depressed.

There are many possible physical and psychological causes of fatigue. Some of the more common are:

• An allergy that leads to hay fever or asthma
• Anemia (including iron deficiency anemia)
• Depression or grief
• Persistent pain
• Sleep disorders such as ongoing insomnia, obstructive sleep apnea, or narcolepsy
• Underactive thyroid or overactive thyroid
• Use of alcohol or illegal drugs like cocaine, especially with regular use

Fatigue can also accompany the following illnesses:

• Addison's disease
• Anorexia or other eating disorders
• Arthritis, including juvenile rheumatoid arthritis
• Autoimmune diseases such as lupus
• Cancer
• Chronic liver or kidney disease
• Congestive heart failure
• Diabetes
• Infection, especially one that takes a long time to recover from or treat such as bacterial endocarditis (infection of the heart muscle or valves), parasitic infections, AIDS, tuberculosis, and mononucleosis
• Malnutrition

Certain medications may also cause drowsiness or fatigue, including antihistamines for allergies, blood pressure medicines, sleeping pills, steroids, and diuretics.

Chronic fatigue syndrome (CFS) is a condition that starts with flu-like symptoms and lasts for 6 months or more. All other possible causes of fatigue are eliminated before this diagnosis is made. Little relieves CFS, including rest.

Here are some tips for reducing fatigue:

• Get adequate, regular, and consistent amounts of sleep each night.
• Eat a healthy, well-balanced diet and drink plenty of water throughout the day.
• Exercise regularly.
• Learn better ways to relax. Try yoga or meditation.
• Maintain a reasonable work and personal schedule.
• Change your stressful circumstances, if possible. For example, switch jobs, take a vacation, and deal directly with problems in a relationship.
• Take a multivitamin. Talk to your doctor about what is best for you.
• Avoid alcohol, nicotine, and drug use.

If you have chronic pain or depression, treating either often helps address the fatigue. However, some antidepressant medications may cause or worsen fatigue. Your medication may have to be adjusted to avoid this problem. DO NOT stop or change any medications without instruction from your doctor.

Stimulants (including caffeine) are NOT effective treatments for fatigue, and can actually make the problem worse when the drugs are stopped. Sedatives also tend to worsen fatigue in the long run.

Call your doctor right away if:

• You are confused or dizzy
• You have blurred vision
• You have little to no urine, or recent swelling and weight gain

Call your doctor if:

• You have ongoing, unexplained weakness or fatigue, especially if accompanied by fever or unintentional weight loss
• You have constipation, dry skin, weight gain, or intolerance to cold
• You wake up and fall back to sleep multiple times through the night
• You have headaches
• You are taking any medications, prescription or non-prescription, or using drugs that may cause fatigue or drowsiness
• You feel sad or depressed
• You have insomnia

Your doctor will obtain your medical history and perform a complete physical examination, with special attention to your heart, lymph nodes, and thyroid. He or she may ask questions about your lifestyle, habits, and feelings.

Questions may include:

• How long have you had fatigue? Did it develop recently or awhile ago?
• Have you had fatigue in the past? If so, does it tend to occur in regular cycles?
• How many hours do you sleep each night? From when until when? Do you awake feeling rested or fatigued? Do you have trouble falling asleep? Do you awake during the night? Do you snore or does someone who sleeps nearby tell you that you snore?
• Do you feel fatigued or tired throughout the day? Does it tend to get worse as the day goes on or stays about the same?
• Do you feel bored, stressed, unhappy, or disappointed?
• How are your relationships?
• Has anyone in your life recently passed away?
• Have you had more activity (mental or physical) lately?
• What is your diet like?
• Do you get regular exercise?
• Do you have any other symptoms like pain, headaches, or nausea?
• Have you had any recent change in appetite (up or down) or weight (up or down)?
• Do you fall asleep uncontrollably during the day?
• Do you take any prescription or non-prescription medications? Which ones?

Diagnostic tests that may be performed include the following:

• Blood tests for anemia, thyroid function, and possible infection.
• Urinalysis

Ressel GW. National Institutes of Health. NIH releases statement on managing pain, depression, and fatigue in cancer. Am Fam Physician. 2003; 67(2): 423-424.

Penninx BW. Anemia and decline in physical performance among older persons. Am J Med. 2003; 115(2): 104-110.

Williams RH, Larsen PR, eds. Williams Textbook of Endocrinology. Amsterdam, Netherlands: Elsevier; 2003.

Gonzalez R. Common Syndromes. In McPhee SJ, Papadakis MA, and Tierney, Jr. LM, eds. Current Medical Diagnosis & Treatment 2007. New York: McGraw-Hill; 2007.

Bennett B, Goldstein D, Friedlanger M, Hickie I, Lloyd A. The experience of cancer-related fatigue and chronic fatigue syndrome: a qualitative and comparative study. J Pain Symptom Manage. 2007; May e-pub.