Weakness of legs caused by diarrhea is considered to be related to blood volume insufficiency, electrolyte disorders, infections and so on. 1. Insufficient blood volume: If diarrhea is severe and frequent, it can lead to a large amount of water loss, resulting in insufficient blood volume, insufficient blood supply to the whole body system, resulting in insufficient blood supply and oxygen supply to the legs, causing weakness of the legs. 2. Electrolyte disorders:Severe and frequent diarrhea can lead to a large number of sodium ions and potassium ions loss, resulting in hyponatremia, hypokalemia, resulting in weakness of the legs. 3. Infections:Gastrointestinal infections, such as gastrointestinal flu attack, the virus will not only infect the gastrointestinal tract, but also invade the whole body muscle system, resulting in general weakness, aches and pains. Diarrhea caused by weakness of the legs should be timely to the hospital, under the guidance of the doctor.