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Health Information and Tools >  Weakness and Fatigue

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Weakness and Fatigue

Overview

Weakness and fatigue are two different things. It's important to know exactly what you mean when you talk with your doctor about how you're feeling. It can help you and your doctor narrow down the possible causes of your symptoms.

Weakness

Weakness is a lack of physical or muscle strength. You feel like you need to use extra effort to move your arms, legs, or other muscles.

General weakness often occurs after you've done too much activity at one time. For instance, maybe you took an extra-long hike. You may feel weak and tired, or your muscles may be sore. These symptoms usually go away within a few days.

In rare cases, muscle weakness may be caused by another health problem. These include:

  • A problem with the minerals (electrolytes) found naturally in the body. Examples are low levels of potassium or sodium.
  • Infections, such as a urinary tract infection or a respiratory infection.
  • Problems with the thyroid gland. This gland regulates the way the body uses energy.
  • Rare nerve disorders, such as Guillain-Barré syndrome.

Muscle weakness that is slowly getting worse needs to be checked by a doctor.

Sudden muscle weakness and loss of function in one area of the body also needs to be checked by a doctor right away. It can be a sign of a stroke or of a problem with the spinal cord or a nerve.

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 may cause fatigue. It 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. It usually doesn't require a visit to a doctor.

Many medicines can cause weakness or fatigue. The use of alcohol, caffeine, or drugs can cause fatigue.

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

  • A decrease in the amount of the substance that carries oxygen in red blood cells (anemia).
  • Problems with the heart, such as coronary artery disease or heart failure.
  • Metabolic disorders, such as diabetes.
  • Problems with the thyroid gland. It regulates the way the body uses energy.
  • Kidney disease and liver disease.

Fatigue is a common symptom of mental health problems, such as anxiety or depression. If you think that your fatigue may be caused by a mental health problem, see your doctor.

Information about Weakness and Fatigue

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

Information about Weakness and Fatigue

Current as of: December 20, 2023

Author: Healthwise Staff

Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.