Hyperkalemia is the medical term for a potassium level in the blood that's higher than is healthy. Potassium is a chemical that nerve and muscle cells need to work. This includes the nerve and muscle cells of the heart. The kidneys help control the amount of potassium in the blood.

A healthy blood potassium level is 3.6 to 5.2 millimoles per liter (mmol/L). Having a blood potassium level higher than 6.0 mmol/L can be a danger. It most often needs treatment right away.