Hypokalemia, or low blood potassium, is caused by frequent vomiting, diarrhea, and use of diuret­ics, as well as low potassium intake. Athletes with high sweat losses are also at risk for potassium defi­ciency, which may result in muscle cramps. Common symptoms of potassium deficiency include muscle weakness and loss of appetite. A rapid change in potassium status or long-term low potassium levels can lead to heart arrhythmias.