Though I don't know the entire root word for potassium, the suffix emia refers to something in the blood. Kalemia is the amount of potassium in the blood. Normally, this value is between 3.5 mEq/L and 5.5 mEq/L in an adult human. Any values below this range are referred to as a state of hypokalemia. Values above are referred to as hyperkalemia.

The kidneys maintain this value, and it is very important that they do so. If the value increases by about 4, to a total of 9.5 mEq/L, this will most likely cause tachycardia, which is a Bad Thing.

These are my interpretation of my lecture notes, but I may have used some references from Hole's Anatomy and Physiology (Shier, Butler, Lewis) and Human Physiology (Vander, Sherman, Luciano)