Potassium is an essential dietary mineral and electrolyte. The food you eat usually supplies all of the potassium you need. However, certain diseases (e.g., kidney disease and gastrointestinal disease with vomiting and diarrhea) and drugs, especially diuretics ('water pills'), remove potassium from the body. Potassium supplements are taken to replace potassium losses and prevent potassium deficiency.
Functioning of the heart, kidneys, muscles, nerves, and digestive system all rely on optimum levels of potassium.