Topic 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 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
doctor.
A stressful emotional situation may also cause fatigue.
This type of fatigue usually clears up when the
stress is relieved.
Many prescription and
nonprescription
medicines can cause weakness or fatigue. The use or
abuse 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.
Myalgic encephalomyelitis/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
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.
