glands potassium elimination is quite similar to the kidney, its excretion is also controlled by aldosterone. Regulation of serum potassium is a function of intake, appropriate distribution between intracellular and extracellular compartments, and effective bodily excretion. In healthy individuals, homeostasis is maintained when cellular uptake and kidney excretion naturally counterbalance a patient's dietary intake of potassium. When kidney function becomes compromised, the ability of the body to effectively regulate serum potassium via the kidney declines. To compensate for this deficit in function, the colon increases its potassium secretion as part of an adaptive response. However, serum potassium remains elevated as the colonic compensating mechanism reaches its limits. Elevated potassium Hyperkalemia develops when there is excess production (oral intake, tissue breakdown) or ineffective elimination of potassium. Ineffective elimination can be hormonal (in aldosterone deficiency) or due to causes in the kidney that impair excretion. Increased extracellular potassium levels result in depolarization of the membrane potentials of cells due to the increase in the equilibrium potential of potassium. This depolarization opens some voltage-gated sodium channels, but also increases the inactivation at the same time. Since depolarization due to concentration change is slow, it never generates an action potential by itself; instead, it results in accommodation. Above a certain level of potassium the depolarization inactivates sodium channels, opens potassium channels, thus the cells become refractory. This leads to the impairment of neuromuscular, cardiac, and gastrointestinal organ systems. Of most concern is the impairment of cardiac conduction, which can cause ventricular fibrillation and/or abnormally slow heart rhythms. Diagnosis To gather enough information for diagnosis, the measurement of potassium must be repeated, as the elevation can be due to hemolysis in the first sample. The normal serum level of potassium is 3.5 to 5mmol/L. Generally, blood tests for kidney function (creatinine, blood urea nitrogen), glucose and occasionally creatine kinase and cortisol are performed. Calculating the trans-tubular potassium gradient can sometimes help in distinguishing the cause of the hyperkalemia. Also, electrocardiography (ECG) may be performed to determine if there is a significant risk of abnormal heart rhythms. Physicians taking a medical history may focus on kidney disease and medication use (e.g. potassium-sparing diuretics), both of which are known causes of hyperkalemia. Definitions Normal serum potassium levels are generally considered to be between 3.5 and 5.3 mmol/L. Levels above 5.5mmol/L generally indicate hyperkalemia, and those below 3.5mmol/L indicate hypokalemia. ECG findings With mild to moderate hyperkalemia, there