Under normal physiological conditions, our body fluids and electrolytes are protected in complete balance in a wonderful, flawless design. Even small deviations occurring in this equilibrium may lead to impairments, which can end in death. Especially in fairly common sodium metabolism disorders, it is the responsibility of the clinician to determine, according to the patient's history and her physical examination of him, whether there is an excess or depletion of volume, and to arrange subsequent treatment. Serum sodium levels of 120, 140, or 150 mEq/L alone should be meaningless to the physician in relation to total body sodium and water content because either hyponatremia or hypernatremia can occur while the patient is hypovolemic, euvolemic, or hypervolemic. For example, administering hypertonic or isotonic saline treatment to a patient with hypervolemic hyponatremia in order to correct the sodium will clinically lead to both an increase in edema and a worsening of the hyponatremia. Treatment of hypo- and hypernatremia must be adjusted separately for each patient based on his age, presence of comorbid conditions, and the speed of development of the severity of clinical signs and symptoms. Adjustments either executed too slowly or too quickly will increase mortality or morbidity. For every patient presenting unexplained symptoms of the muscular, skeletal, or neurological systems, including confusion, making the first priority the conduction of electrolyte analyses and the correctly managed effective treatment of excesses or deficiencies may save lives and will certainly save time and money that would otherwise have been spent unnecessarily.