Weakness and fatigue are terms that are often interchanged but in fact 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 health professional narrow down the possible causes of your symptoms.
Weakness is a lack of physical or muscle strength and the feeling that extra effort is needed to perform daily activities that require you to move your arms, legs, or other muscles. Fatigue is a feeling of tiredness, exhaustion, or lack of energy.
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 evaluated.
General weakness often occurs after you have overexerted yourself, such as by taking an extra-long hike. You may feel weak and tired or your muscles may be sore. These sensations usually clear up within a few days. Rarely, generalized muscle weakness may be caused by another health problem, such as:
Muscle weakness that is getting progressively worse requires a visit to a health professional. 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.
General weakness or deconditioning of the body can produce dizziness.
Gradually increasing weakness is a sign of ketosis. The May 2004 Annals of Internal Medicine study showed that most of the Atkins Dieters suffered significantly more general weakness.
The sensation of weakness, especially muscle weakness, may be due to the loss of muscle mass seen in andropause.
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