Chloride (Cl)

What is chloride?

Chloride is an important negatively charged electrolyte found in the blood and in the fluid between cells. Together with sodium, it helps regulate the amount of fluid in the body and blood pressure, and together with bicarbonate, it helps maintain the acid-base balance of the blood. It is also part of the stomach acid involved in digestion.

The body gets chloride mainly from table salt (sodium chloride) and salty foods; the excess is excreted by the kidneys, and some is lost through sweat and stool. The chloride test measures the amount of chloride in blood serum, and the result is reported in mmol/L. The measurement is usually made with ion-selective electrodes and is often run together with sodium, potassium and bicarbonate as an electrolyte panel.

When is a chloride test ordered?

Chloride is rarely ordered on its own; it is usually part of a routine biochemistry or electrolyte panel. The result is interpreted together with the other electrolytes, particularly when fluid loss, kidney problems and acid-base imbalances are being assessed. It is one of the tests frequently checked in emergencies and in hospitalized patients.

It may be repeated at regular intervals to monitor electrolyte balance in people receiving IV fluids, taking diuretics, or being followed for heart, kidney or liver disease. Using the chloride value together with sodium and bicarbonate, the doctor can also calculate what is known as the anion gap.

• Prolonged vomiting or diarrhea
• Weakness, confusion or signs of dehydration
• Monitoring of kidney disease and diuretic therapy
• Suspected acid-base imbalance
• Monitoring of heart failure, liver disease or hormonal disorders

How do I prepare for a chloride test?

No special preparation or fasting is needed for a chloride test, and the blood sample can be given at any time of day. If other tests that require fasting will be run on the same sample, simply follow your doctor's instructions. Keep drinking water as usual before the test; severe fluid restriction or drinking very large amounts of fluid can affect the result.

Diuretics, corticosteroid medications, some stomach medications and saline solutions given intravenously can change chloride levels. Writing down the names and doses of the medications you take regularly and sharing them with your doctor helps ensure that the result is interpreted correctly. Mentioning any recent vomiting, diarrhea or heavy sweating also makes interpretation easier. Blood is drawn from a vein on the inside of the arm within a few minutes; our nurse can come to your home or workplace for this.

What does a chloride result mean?

High chloride is most often associated with the body losing water, prolonged diarrhea, certain kidney diseases, or conditions in which the blood shifts toward the acidic side. Receiving large amounts of IV saline can also raise the level. Chloride levels usually move in parallel with sodium. Mild changes often cause no symptoms; with marked imbalances, however, weakness, muscle cramps, nausea or changes in breathing may occur.

Low chloride, on the other hand, can be seen in conditions such as prolonged vomiting, heavy sweating, diuretic use, heart failure, certain lung diseases or excess water retention in the body. A chloride value alone does not establish a diagnosis; the doctor evaluates the result together with sodium, potassium and bicarbonate to look for the cause of the imbalance. The reference range may vary depending on the method and the laboratory used; age and sex can also affect the result, and this page shows the range of the laboratory that analyzes your sample. For this reason, you should have your chloride value interpreted by a doctor who can consider it together with your symptoms and other tests.