Fatigue is one of the most common symptoms in MS and the majority of people with MS experience it at one time or another. MS fatigue is different than normal fatigue and science has not yet been able to explain what causes it.

Some of the fatigue people with MS experience might be caused by sleep disruption from a malfunctioning bladder, or perhaps from expending a lot of energy completing tasks — such as getting dressed — when they are experiencing muscle weakness. Other possible causes of fatigue are depression, medications, or other medical conditions, such as anemia and thyroid disease. But beyond these causes, there does seem to be an MS-related fatigue that often gets worse as the day progresses, is more severe than normal fatigue, and occurs whether or not you've had a good night's sleep.

Eighty to ninety percent of people with MS report fatigue as a symptom. For about two-thirds, fatigue sometimes limits daily activities.