Hyperkalemia is a condition caused by an abnormally high concentration of potassium in the blood. Potassium is a key element in contraction of muscles (including the heart) and for the functioning of many complicated proteins (enzymes). Potassium is found primarily in the skeletal muscle and bone, and participates with sodium to contribute to the normal flow between the body fluids and the cells of the body (homeostasis). The concentration of potassium in the body is regulated by the kidneys, and balance is maintained through excretion in urine. When the kidneys are functioning normally, the amount of potassium in the diet is usually sufficient for use by the body and the excess is excreted. Chemical and hormonal influences also help regulate the internal potassium balance. When hyperkalemia occurs, there is an imbalance resulting from a dysfunction of these normal processes.
Normally, 98% of the potassium in the body is found in the cells of various tissues, while only about 2% is circulating in the blood. When hyperkalemia occurs, it may come about because of an increase in total body potassium or as a result of increased release of potassium from the cells to the blood.
Abnormally high levels of potassium in the blood or urine suggest the presence of another underlying medical condition. Because potassium helps to regulate muscle activity, including the activity of heart (cardiac) muscle, hyperkalemia needs to be taken seriously.