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.
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 only be determined when other symptoms are
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:
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
transient ischemic attack) or
spinal cord or with a specific nerve in the body.
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 the 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
A stressful emotional situation may also cause fatigue.
This type of fatigue usually clears up when the
stress is relieved.
Many prescription and
medicines can cause weakness or fatigue. The use or
abuse of alcohol, caffeine, or illegal drugs can cause fatigue.
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
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:
Chronic fatigue syndrome is an uncommon
cause of severe, persistent fatigue.
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
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.
Check your symptoms to decide if and when
you should see a doctor.
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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
If generalized weakness and fatigue are not related to another
illness, follow the guidelines in the Prevention section and be patient. It may
take a while for you to feel energetic again.
Call your doctor if any of the following occur during home
Mild fatigue can often be prevented by
changes in lifestyle habits.
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
While you are waiting for your appointment, it may be helpful
to keep a
diary of your symptoms(What is a PDF document?).
January 12, 2011
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine
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