Ask the doctors: Is a high potassium level bad?

Q. My potassium level is high, and my physician stopped the medication that has successfully controlled my blood pressure for years, lisinopril. What is the danger from high potassium, and why is lisinopril a problem?

A. Potassium is important for the electrical activity of the cells in your heart, and levels that are below 3.4 milligrams per deciliter (mg/dL) or above 5.0 mg/dL can lead to heart rhythm problems that may be life-threatening. Some medications used for high blood pressure, heart failure, and other cardiovascular problems can affect potassium levels, so levels must be checked often.