Electrolyte concentrations can easily be measured in blood and urine samples. The concentration of potassium in the serum is maintained within a very narrow range, 3.5 to 5.0 milliequivalents per liter, to keep the body functioning normally. Blood-test results that show the quantity of potassium in serum to be outside this normal range tells physicians that the amount of potassium in the cells is too high or too low, suggesting a disease state. An abnormally high concentration of potassium in serum is known as hyperkalemia. In general, an increased serum potassium concentration is more dangerous than a low concentration.
Elevated potassium affects all cells of the body but particularly nerves and muscles.
As a result, a person may feel weak and the heart may not pump enough blood. When the muscles of the intestines are involved, it may lead to distention and diarrhea. Hyperkalemia can be caused by either excessive intake or decreased excretion of potassium. It can also be caused by potassium moving out of the cells into surrounding fluids. As you might expect, the causes of hypokalemia are just the opposite of those of hyperkalemia, e.g., decreased potassium intake, movement of potassium into the cells, and over-excretion or other potassium loss.