Overview

Weakness and fatigue are terms that are often used as if they mean the same thing. But in fact they describe two different sensations. It is important to know exactly what you mean when you say "I feel weak" or "I am fatigued" because it can help you and your doctor narrow down the possible causes of your symptoms.

• Weakness is a lack of physical or muscle strength and the feeling that extra effort is required to move your arms, legs, or other muscles. If muscle weakness is the result of pain, the person may be able to make muscles work, but it will hurt.
• Fatigue is a feeling of tiredness or exhaustion or a need to rest because of lack of energy or strength. Fatigue may result from overwork, poor sleep, worry, boredom, or lack of exercise. It is a symptom that may be caused by illness, medicine, or medical treatment such as chemotherapy. Anxiety or depression can also cause fatigue.

Both weakness and fatigue are symptoms, not diseases. Because these symptoms can be caused by many other health problems, the importance of weakness and fatigue can be determined only when other symptoms are evaluated.

Weakness

General weakness often occurs after you have done too much activity at one time, such as by taking an extra-long hike. You may feel weak and tired, or your muscles may be sore. These sensations usually go away within a few days.

In rare cases, generalized muscle weakness may be caused by another health problem, such as:

• A problem with the minerals (electrolytes) found naturally in the body, such as low levels of potassium or sodium.
• Infections, such as a urinary tract infection or a respiratory infection.
• Problems with the thyroid gland, which regulates the way the body uses energy.
  • A low thyroid level (hypothyroidism) can cause fatigue, weakness, lethargy, weight gain, depression, memory problems, constipation, dry skin, intolerance to cold, coarse and thinning hair, brittle nails, or a yellowish tint to the skin.
  • A high thyroid level (hyperthyroidism) can cause fatigue, weight loss, increased heart rate, intolerance to heat, sweating, irritability, anxiety, muscle weakness, and thyroid enlargement.
• Guillain-Barré syndrome, a rare nerve disorder that causes weakness in the legs, arms, and other muscles and that can progress to complete paralysis.
• Myasthenia gravis, a rare, chronic disorder that causes weakness and rapid muscle fatigue.

Muscle weakness that is slowly getting worse requires a visit to a doctor.

Sudden muscle weakness and loss of function in one area of the body can indicate a serious problem within the brain (such as a stroke or transient ischemic attack) or spinal cord or with a specific nerve in the body.

Fatigue

Fatigue is a feeling of tiredness, exhaustion, or lack of energy. You may feel mildly fatigued because of overwork, poor sleep, worry, boredom, or lack of exercise. Any illness, such as a cold or influenza (flu), may cause fatigue, which usually goes away as the illness clears up. Most of the time, mild fatigue occurs with a health problem that will improve with home treatment and does not require a visit to a doctor.

A stressful emotional situation may also cause fatigue. This type of fatigue usually clears up when the stress is relieved.

Many prescription and non-prescription medicines can cause weakness or fatigue. The use of alcohol, caffeine, or illegal drugs can cause fatigue.

A visit to a doctor usually is needed when fatigue occurs along with more serious symptoms, such as increased breathing problems, signs of a serious illness, abnormal bleeding, or unexplained weight loss or gain.

Fatigue that lasts longer than 2 weeks usually requires a visit to a doctor. This type of fatigue may be caused by a more serious health problem, such as:

• A decrease in the amount of oxygen-carrying substance (hemoglobin) found in red blood cells (anemia).
• Problems with the heart, such as coronary artery disease or heart failure, that limit the supply of oxygen-rich blood to the heart muscle or the rest of the body.
• Metabolic disorders, such as diabetes, in which sugar (glucose) remains in the blood rather than entering the body's cells to be used for energy.
• Problems with the thyroid gland, which regulates the way the body uses energy.
  • A low thyroid level (hypothyroidism) can cause fatigue, weakness, lethargy, weight gain, depression, memory problems, constipation, dry skin, intolerance to cold, coarse and thinning hair, brittle nails, or a yellowish tint to the skin.
  • A high thyroid level (hyperthyroidism) can cause fatigue, weight loss, increased heart rate, intolerance to heat, sweating, irritability, anxiety, muscle weakness, and thyroid enlargement.
• Kidney disease and liver disease, which cause fatigue when the concentration of certain chemicals in the blood builds up to toxic levels.

If fatigue occurs without an obvious cause, it is important to evaluate your mental health. Fatigue is a common symptom of mental health problems, such as anxiety or depression. Fatigue and depression may become so severe that you may consider suicide as a way to end your pain. If you think your fatigue may be caused by a mental health problem, see your doctor.

Home Treatment

If you have generalized weakness and fatigue along with other symptoms, evaluate those symptoms. Home treatment for your other symptoms usually will improve your weakness and fatigue. Mild generalized weakness and fatigue that occur with a viral illness usually improve with the following home treatment measures.

• Get extra rest while you are ill. Let your symptoms be your guide.
  • If you have a cold, you may be able to stick to your usual routine and just get some extra sleep.
  • If you have the flu, you may need to spend a few days in bed.
• Return to your usual activities slowly to avoid prolonging the fatigue.
• Be sure to drink extra fluids to avoid dehydration.

• Listen to your body. Alternate rest with exercise. Gradually increasing your exercise may help decrease your fatigue.
• Limit medicines that might contribute to fatigue. Tranquilizers and cold and allergy medicines often cause fatigue.
• Improve your diet. Eating a balanced diet may increase your energy level. Do not skip meals, especially breakfast.
• Reduce your use of alcohol or other drugs, such as caffeine or nicotine, which may contribute to fatigue.
• Cut back on watching television. Spend that time with friends, try new activities, or travel to break the fatigue cycle.
• Get a good night's sleep. This may be the first step toward controlling fatigue.
  • Eliminate all sound and light disturbances.
  • Do not eat just before you go to bed.
  • Use your bed only for sleeping. Do not read or watch TV in bed.
    • For more information, see Insomnia: Improving Your Sleep.

Symptoms to watch for during home treatment

Call your doctor if any of the following occur during home treatment:

• New symptoms develop along with the weakness and fatigue.
• Symptoms last longer than 2 weeks.
• Symptoms become more severe or more frequent.

Prevention

Mild fatigue can often be prevented by changes in lifestyle habits.

• Get regular exercise. If you feel too tired to exercise vigorously, try taking a short walk.
• Eat a balanced diet. Do not skip meals, especially breakfast.
• Get enough sleep.
• Deal with emotional problems instead of ignoring or denying them.
• Take steps to control your stress and workload. For more information, see the topic Stress Management.

Preparing For Your Appointment

To prepare for your appointment, see the topic Making the Most of Your Appointment.

You can help your doctor diagnose and treat your condition by being prepared to answer the following questions:

• What is your major symptom, weakness or fatigue?
• Have you had these symptoms before? If so:
  • Did you see a doctor for an evaluation of your symptoms?
  • What was the diagnosis?
  • How were your symptoms treated?
• What other symptoms do you have that may be related to your major symptom?
• How long have you had your symptoms? Describe what was happening when you first noticed your symptoms.
• What makes your symptoms better or worse?
• What home treatment have you tried?
• Are you experiencing any particular stress at home, work, or school that could be causing your weakness or fatigue?
• Are you using any alcohol or other drugs, such as caffeine or nicotine, that may be causing fatigue?
• What medicines have you used, both prescription and non-prescription?
• Do you have any health risks?

While you are waiting for your appointment, it may be helpful to keep a diary of your symptoms .