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 5.5 mmol/L generally indicate hyperkalemia, and those below 3.5 mmol/L indicate hypokalemia. ECG findings
With mild to moderate hyperkalemia, there is prolongation of the PR interval and development of peaked T waves. Severe hyperkalemia results in a widening of the QRS complex, and the ECG complex can evolve to a sinusoidal shape. There appears to be a direct effect of elevated potassium on some of the potassium channels that increases their activity and speeds membrane repolarisation. Also, (as noted above), hyperkalemia causes an overall membrane depolarization that inactivates many sodium channels. The faster repolarisation of the cardiac action potential causes the tenting of the T waves, and the inactivation of sodium channels causes a sluggish conduction of the electrical wave around the heart, which leads to smaller P waves and widening of the QRS complex. Some of potassium currents are sensitive to extracellular potassium levels, for reasons that are not well understood. As the extracellular potassium levels increase, potassium conductance is increased so that more potassium leaves the myocyte in any given time period.
Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels above 5.5 mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasionally when severe it can cause palpitations, muscle pain, muscle weakness, or numbness. Hyperkalemia can cause an abnormal heart rhythm which can result in cardiac arrest and death.Common causes of hyperkalemia include kidney failure, hypoaldosteronism, and rhabdomyolysis. A number of medications can also cause high blood potassium including spironolactone, NSAIDs, and angiotensin converting enzyme inhibitors. The severity is divided into mild (5.5–5.9 mmol/L), moderate (6.0–6.4 mmol/L), and severe (>6.5 mmol/L). High levels can be detected on an electrocardiogram (ECG). Pseudohyperkalemia, due to breakdown of cells during or after taking the blood sample, should be ruled out.Initial treatment in those with ECG changes is salts, such as calcium gluconate or calcium chloride. Other medications used to rapidly reduce blood potassium levels include insulin with dextrose, salbutamol, and sodium bicarbonate. Medications that might worsen the condition should be stopped and a low potassium diet should be started. Measures to remove potassium from the body include diuretics such as furosemide, potassium-binders such as polystyrene sulfonate and sodium zirconium cyclosilicate, and hemodialysis. Hemodialysis is the most effective method.Hyperkalemia is rare among those who are otherwise healthy. Among those who are  hospitalized, rates are between 1% and 2.5%.