Pathophysiology of Potassium Metabolism

The daily intake of potassium in an average American diet is about 100 mEq. Virtually all of the potassium ingested is absorbed by the gut (less than 10 mEq are excreted in stools) and maintenance of external balance requires the daily renal excretion of an amount of potassium identical to that absorbed from the gut. Potassium is the major cation of the intracellular fluid space. The body distribution of potassium is depicted in Figure 1. Total body content of potassium is approximately 3700 mEq, of which only 50-70 mEq are distributed in the extracellular fluid (ECF), the remainder being confined to the intracellular fluid space (ICF). The bulk of the ICF potassium is contained in muscle cells (≃2800 mEq) and comparably smaller quantities are distributed in skin (≃500 mEq), liver cells (≃100 mEq), and red blood cells (≃250 mEq).