normokalemia

Normokalemia is the condition in which a person’s serum potassium concentration falls within the normal reference range. In clinical practice, this range is typically 3.5 to 5.0 milliequivalents per liter (mEq/L), equivalent to 3.5 to 5.0 millimoles per liter (mmol/L). A single measurement within this range is not inherently diagnostic of whole-body potassium status, but it indicates that circulating potassium is not at overtly high or low levels at that time.

Potassium is the major intracellular cation, with about 98% of total body potassium residing inside cells and only a small amount in the extracellular fluid. Serum potassium reflects a balance among dietary intake, cellular distribution, and renal excretion. Potassium helps establish the resting membrane potential of cells, especially excitable tissues like nerves and muscles. Because cell-to-cell distribution is sensitive, small shifts in serum potassium can significantly affect electrical activity and cellular function; both hypokalemia and hyperkalemia can have serious consequences.

Regulation is primarily renal, with aldosterone promoting potassium excretion. Factors such as insulin and beta-adrenergic activity drive potassium into cells, while acid–base status can alter distribution (acidosis tends to raise extracellular potassium; alkalosis lowers it). Medications and conditions that affect intake, losses, or redistribution can influence serum potassium without necessarily changing overall body potassium stores.

Clinical interpretation requires context. Normal serum potassium does not exclude total body potassium depletion or excess, particularly with ongoing losses, shifts, or redistribution. Serial measurements and clinical correlation are important in patients on diuretics, renal disease, insulin therapy, or other treatments that affect potassium balance. See also hypokalemia and hyperkalemia.