Potassium is a mineral that plays many critical roles in the body. Food sources of potassium include fruits (especially dried fruits), cereals, beans, milk, and vegetables. Potassium is used for treating and preventing low potassium levels. It is also used to treat high blood pressure and prevent stroke. Some people use it to treat high levels of calcium, a type of dizziness called MeniÃ¨re's disease, thallium poisoning, insulin resistance, symptoms of menopause, and infant colic.