Potassium (pronounced /pəˈtæsiəm/) is a chemical element. It has the symbol K (Arabic: al qalja → Latin: kalium) and atomic number 19. The name "potassium" comes from the word "potash", as potassium was first isolated from potash. Potassium is a soft silvery-white metallic alkali metal that occurs naturally bound to other elements in seawater and many minerals. It oxidizes rapidly in air and is very reactive, especially towards water. In many respects, potassium and sodium are chemically similar, although organisms in general, and animal cells in particular, treat them very differently.
Potassium is found in the human body and is necessary for the proper transmission of nerve impulses. Low potassium levels will usually result in fainting, unconsciousness and coma in severe cases. High potassium will result in extremely high blood pressure and the danger of stroke.
Potassium is found in many food sources, particularly bananas, oranges and potatoes. It is also found in most sports drinks. Most people have no difficulty managing their potassium levels. Potassium is usually disposed of through urination and sweat as potassium compounds are very water soluble and pass through the kidneys along with water.
However, dialysis will not remove potassium in sufficient quantities. As such, dialysis patients must avoid foods containing potassium.
Patients taking diuretics, those with urination disorders such as diabetes insipidus, and individuals who engage in heavy exercise in humid conditions have the opposite problem - frequent urination and profuse sweating tends to remove potassium from the body quickly, making it vital that it be replaced through dietary sources. Most diuretics contain a potassium supplement for this purpose.