Hypokalemia refers to a lower than normal potassium level in your bloodstream. Potassium helps carry electrical signals to cells in your body. It is critical to the proper functioning of nerve and muscle cells, particularly heart muscle cells. Normally, your blood potassium level is 3.6 to 5.2 millimoles per liter (mmol/L). Low potassium symptoms may include fatigue, weakness, muscle cramps, and constipation. A very low potassium level (less than 2.5 mmol/L) can be life-threatening and requires urgent medical attention. Only about 17% of patients overall with primary aldosteronism experience hypokalemia, but it is more common if you have an aldosterone-producing adenoma (APA). About half the patients with an APA experience hypokalemia.