Hyperkalemia (AE) or Hyperkalaemia (BE) is an elevate blood level of the electrolyte potassium. The prefix hyper- means high (contrast with hypo-, meaning low). The middle kal refers to kalium, which is neo-Latin for potassium. The end portion of the word, -emia, means "in the blood". Extreme degrees of hyperkalemia are considered a medical emergency due to the risk of potentially fatal arrhythmias.