Blood potassium levels are closely regulated since both high and low levels can have life-threatening consequences. A normal potassium blood level is typically 3.5 to 5 milliequivalents per liter, or mEq/L. The normal range may vary slightly among testing laboratories, however.

Furosemide is used to treat high blood pressure, liver disease and fluid retention. This medication affects the composition of the urine and can lead to changes in the levels of electrolytes, including potassium.