Measurement of chloride ion levels is never ordered alone; it is nearly always part of an electrolyte panel, including sodium, potassium, and sometimes bicarbonate (total CO2) testing. Generally, sodium and chloride ion levels change at the same time.
A high level of chloride ions (hyperchloremia) and sodium (hypernatremia) in the blood usually indicates dehydration (water loss in the urine or stool) that is not offset by drinking lots of water, but it can also indicate a kidney problem or overactive adrenal glands (Cushing’s disease). Hyperchloremia also occurs in disorders that affect the blood pH: neutralization of acids by bicarbonate in the blood (metabolic acidosis) or loss of carbonic gas by breathing too quickly (hyperventilation).
A low level of chloride ions (hypochloremia) and sodium (hyponatremia) occurs in any condition causing a drop in the blood sodium level. Congestive heart failure, prolonged vomiting, excessively low adrenal gland function (Addison’s disease), emphysema, or other chronic pulmonary diseases are causes of hyponatremia and hypochloremia. Hypochloremia also accompanies a loss of acid by the body (metabolic alkalosis).