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You are here : 3-RX.com > Medical Encyclopedia > Medical Symptoms > Weakness


Alternate Names : Asthenia

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

Weakness is usually defined as a lack of or decrease in muscle strength. It is different from fatigue, which is a loss of energy.

What is going on in the body?

Weakness can be used to describe a mental and physical state in which someone doesn't have the muscle strength, for example, to walk. It is common and sometimes difficult to evaluate. Weakness has many causes.

What are the causes and risks of the condition?

Weakness has many causes that are best grouped into these categories:

  • muscle problems, such as deconditioning or a lack of exercise, muscle injuries or inherited muscle defects, such as muscular dystrophy
  • nerve problems, possibly nerve damage from injury or from toxins such as lead poisoning or alcohol dependence
  • nerve damage such as diabetic neuropathy
  • vitamin deficiencies, such as lack of vitamin B12
  • spinal cord injuries or other disorders
  • salt imbalances, such as a low sodium level, called hyponatremia, or a high potassium level, called hyperkalemia
  • brain problems, such as a stroke or a condition called Parkinsonism, which affects the ability to move
  • autoimmune disorders, which occur when people's immune systems attack their own bodies for unknown reasons. Some examples are multiple sclerosis, which causes inflammation and damage to the brain and myasthenia gravis, which causes muscle weakness that often gets worse toward the end of the day
  • hormone imbalances, such as low thyroid hormone levels, called hypothyroidism, or low adrenal hormone levels, called hypoadrenalism
  • any infection, especially infectious mononucleosis, flu, poliomyelitis, botulism or pneumonia
  • any serious diseases, such as congestive heart failure, cirrhosis, chronic renal failure, or cancer
  • psychiatric conditions, especially depression
  • chronic fatigue syndrome and fibromyalgia, two poorly understood conditions with no known cause that commonly make people feel weak and tired
  • Other causes are also possible. Sometimes, no cause is found.


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    Weakness: Symptoms & Signs

    Author: Adam Brochert, MD
    Reviewer: Eileen McLaughlin, RN, BSN
    Date Reviewed: 08/09/01

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