人體內鉀離子(K+) 靠細胞間快速的轉移，與腎臟調節每日鉀離子的排泄，來維持急性與慢性的恆定。低血鉀(hypokalemia) 主要為鉀離子大量快速往細胞內移動，或腎臟及非腎臟因素的鉀離子流失過多所導致。低血鉀可能會增加心臟血管疾病患者的罹病率及死亡率，導致心律不整(cardiac arrhythmias)、肌肉癱瘓甚至呼吸停止，因此如何快速的診斷與治療低血鉀是本篇探討的主題。其病因可以依尿液鉀離子的排泄量(potassium (K+) excretion)、血中酸鹼值、血壓高低、血漿腎素活性(renin activity)、醛固酮(aldosterone) 濃度、皮質類固醇(cortisol)濃度，及尿液中鈉離子與氯離子的濃度而進一步鑑別診斷。低尿液鉀離子排泄可為鉀離子急性往細胞內移動，腸道鉀離子流失或之前腎臟過度排泄所引起。而高尿液鉀離子排泄則通常合併有酸鹼異常。低血鉀的治療，主要取決於低血鉀的程度、造成低血鉀的快慢、臨床症狀、潛在病因及其他相關的潛在危險因子。

The concentration of potassium (K+) in plasma is determined on a rapid distribution of K+ between intracellular and extracellular fluid (ECF) compartments and on a day-to-day basis by the renal excretion of K+. Accordingly,hypokalemia usually arises from a shift of K+ into cells and/or excessive renal (or extrarenal) K+ loss. Further,hypokalemia is associated with increased morbidity and mortality in patients with cardiovascular disease. It may provoke cardiac arrhythmias and/or respiratory arrest. Our aim is to suggest better diagnostic tools and therapeutic principles. The measurement of urine K+ excretion rate by spot and/or 24-hour urine to evaluate K+ excretion, the acid-base status in blood, the level of blood pressure, plasma renin activity, plasma aldosterone concentration,cortisol levels and the urine sodium (Na+) and chloride (Cl-) concentration can help differentiate among the various
causes of hypokalemia. In patients with a low rate of K+ excretion, hypokalemia can be explained by an acute shift of K+ into cells, intestinal K+ loss, or prior renal K+ excretion. Patients with a high rate of K+ excretion usually have metabolic acid-base disorders. The treatment of hypokalemia depends on the degree and timing of hypokalemia,
clinical manifestations, the underlying causes, and potential risks attributable to associated conditions.