Hyperkalemia (hyperkalaemia in British English, hyper- high; kalium, potassium; -emia, "in the blood") refers to an elevated concentration of the electrolyte potassium (K) in the blood. The symptoms of elevated potassium are nonspecific, and the condition is usually discovered in a blood test performed for another reason. Extreme hyperkalemia is a medical emergency, due to the risk of potentially fatal abnormal heart rhythms (arrhythmia).