It is common and sometimes difficult to evaluate. Weakness has many causes. Weakness itself may be a symptom. 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.
Prevention depends on the cause.
For example, weakness due to lack of exercise can be prevented with regular exercise. Weakness due to alcohol or diabetic neuropathy can be prevented by not drinking alcohol or controlling diabetes with a proper diet and medications. Many cases of weakness cannot be prevented. Figuring out the cause of weakness starts with a history and physical exam. In some cases, this may be all that the healthcare provider needs to make a diagnosis.