Blood chloride is used, along with sodium, to evaluate problems with the acid-base balance in the body, and to monitor treatment. In persons with too much base, urine chloride measurements can tell the doctor whether the cause is loss of salt (in cases of dehydration, vomiting, or use of diuretics, where urine chloride would be very low), or an excess of certain hormones such as cortisol or aldosterone (where urine chloride would be high). Urine tests for chloride are also used, along with sodium, to monitor persons put on a low-salt diet. If sodium and chloride levels are high, the doctor knows that the patient is not following the diet.

A blood chloride test is usually ordered as part of an electrolyte panel or a basic metabolic panel. It is almost never ordered by itself. If your sodium measurement is abnormal, the doctor will look at whether the chloride measurement changes in the same way. This helps the doctor know if there is also a problem with acid or base and helps him/her to guide treatment. Urine chloride is usually performed along with sodium in evaluating the cause of low or high blood levels. It is also helpful in persons with too much base (alkalosis) to help determine the cause.

A severe elevation or loss of this electrolyte indicates a serious fluid and electrolyte imbalance. Medical staff must take immediate action to restore the electrolyte balance. The type of medical treatment depends on the cause of the problem.

Increased levels of chloride (called hyperchloremia) usually indicate dehydration, but can also occur with any other problem that causes high blood sodium. Hyperchloremia also occurs when too much base is lost from the body (producing metabolic acidosis), or when a person hyperventilates (causing respiratory alkalosis).

Decreased levels of chloride (called hypochloremia) occur with any disorder that causes low blood sodium. Hypochloremia also occurs with prolonged vomiting or gastric suction, chronic diarrhea, emphysema, or other chronic lung disease (causing respiratory acidosis), and with loss of base from the body (called metabolic alkalosis).

PLEASE NOTE: Numerically reported test results are interpreted according to the test's reference range, which may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. A specific result within the reference (normal) range – for any test – does not ensure health just as a result outside the reference range may not indicate disease. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. To learn the reference range for your test, consult your doctor or laboratorian. Lab Tests Online recommends you consult your physician to discuss your test results as a part of a complete medical examination.

Drugs that affect sodium will also cause changes in chloride. In addition, swallowing large amounts of baking soda or substantially more than the recommended dosage of antacids can also cause low chloride.

Some instructions for routine testing advise patients to stop all food and fluids for eight hours before the test to prevent the normal drop in chloride value after eating.