Blood chloride testing is frequently ordered, along with other electrolytes, as part of a regular physical. These tests may also be ordered to evaluate symptoms such as prolonged vomiting, diarrhea, weakness, and respiratory distress. If an electrolyte imbalance is detected, the doctor will look for and address the disease, condition, or medication causing the imbalance and may order electrolyte testing at regular intervals to monitor the effectiveness of treatment. If an acid-base imbalance is suspected, the doctor may also order blood gas tests to further evaluate the severity and cause of the imbalance.

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.

The blood chloride test is almost never ordered by itself. It is usually ordered as part of an electrolyte panel, a basic metabolic panel, or a comprehensive metabolic panel, which are ordered frequently as part of a routine physical or evaluation of a patient with an acute or chronic illness. Some of these tests may be ordered at regular intervals when a patient has a disease or condition or is taking a medication that can cause an electrolyte imbalance. Electrolyte panels or basic metabolic panels are commonly used to monitor treatment of certain problems, including high blood pressure, heart failure, and liver and kidney disease.

A urine chloride test may be performed along with a blood or urine sodium when evaluating the cause of low or high blood chloride levels. The doctor will look at whether the chloride measurement changes mirror those of the sodium. This helps the doctor determine if there is also an acid-base imbalance and helps to guide treatment.

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 acid from the body (called metabolic alkalosis).

NOTE: The result of your chloride test is measured by your doctor against a reference range for the test to determine whether the result is “normal” (it is within the range of numbers), high (it is above the high end of the range), or low (it is below the low end of the range). Because there can be many variables that affect the determination of the reference range, the reference range for this test is specific to the lab where your test sample is analyzed. For this reason, the lab is required to report your results with an accompanying reference range. Typically, your doctor will have sufficient familiarity with the lab and your medical history to interpret the results appropriately.

While there is no such thing as a “standard” reference range for chloride, most labs will report a similar, though maybe not exactly the same, set of numbers as that included in medical textbooks or found elsewhere online. For this reason, we recommend that you talk with your doctor about your lab results. For general guidance only, we are providing the reference range for this test from the classic medical text, Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.

For more information on reference ranges, please read Reference Ranges and What They Mean.

Drugs that affect sodium blood levels 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.