Hyperkalemia, also spelled hyperkalaemia, is an elevated level of potassium (K+) in the blood serum.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 this results in no symptoms. Occasionally when severe it results in palpitations, muscle pain, muscle weakness, or numbness.An abnormal heart rate can occur which can result in cardiac arrest and death. Common causes include kidney failure, hypoaldosteronism, and rhabdomyolysis. A number of medications can also cause high blood potassium including spironolactone, NSAIDs, and angiotensin converting enzyme inhibitors.