what is a hypokalemia
By Mayo Clinic Staff. Low potassium (hypokalemia) refers to a lower than normal potassium level in your bloodstream. Potassium is a chemical (electrolyte) that is critical to the proper functioning of nerve and muscles cells, particularly heart muscle cells. Normally, your blood potassium level is 3.6 to 5.2 millimoles per liter (mmol/L).