Hyperkalemia, also known as hyperpotassemia, is the presence of abnormally high levels of potassium in the blood. The majority of the body's potassium is found in the tissue cells and is vital in regulation and function of muscle activity, including that of the heart. Consequently, hyperkalemia is a serious condition that should be treated immediately. 

Symptoms of hyperkalemia include fatigue and weakness, nausea or vomiting, breathing issues, chest pains, heart palpitations or arrhythmia, and a numb or tingling sensation. 

Hyperkalemia is often a sign of an underlying medical condition, such as Addison's disease, kidney failure, or diabetes type 1. It may also be caused by dehydration, internal bleeding or certain medications, including some angiotensin converting enzyme inhibitors/ACEIs and angiotensin-II receptor blockers/ARBs and other combinations. 

Treatment of hyperkalemia focuses on ridding the body of excess potassium and stabilizing the heart. When the condition is the result of kidney failure, patients may need hemodialysis to filter excess potassium from the blood. Medication, for example, antidotes and adsorbents such as Kayexalate (kionex, sodium polystyrene sulfonate), may also be prescribed.