Chloride

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Also known as:  Cl
Formal name: Chloride

At a Glance

Why Get Tested?

To determine if there is a problem with your body's electrolyte balance or acid-base balance and to monitor treatment

When to Get Tested?

As part of a standard electrolyte panel or metabolic panel or if your doctor thinks that you have an electrolyte imbalance

Sample Required?

A blood sample drawn from a vein in the arm; sometimes a random or 24-hour urine sample

Test Preparation Needed?

None

The Test Sample

What is being tested?

Chloride is an electrolyte. It is a negatively charged ion that works with other electrolytes, such as potassium, sodium, and bicarbonate, to help regulate the amount of fluid in the body and maintain the acid-base balance. Chloride is present in all body fluids but is found in the highest concentration in the blood and in the fluid outside of the body’s cells. Most of the time, chloride concentrations mirror those of sodium, increasing and decreasing for the same reasons and in direct relationship to sodium. When there is an acid-base imbalance, however, blood chloride levels can change independently of sodium levels as chloride acts as a buffer. It helps to maintain electrical neutrality at the cellular level by moving into or out of the cells as needed.

Chloride is taken into the body through food and table salt, which is made up of sodium and chloride ions. Most of the chloride is absorbed by the gastrointestinal tract, and the excess is excreted in urine. The normal blood level remains steady, with a slight drop after meals (because the stomach produces acid after eating, using chloride from blood).

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm. Chloride can also be measured in a random or 24-hour urine sample.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Institute of Medicine. Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate. Available online at http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx through http://www.iom.edu. Accessed September 2011. 

Pagana and Pagana. Mosby’s Manual of Diagnostic and Laboratory Tests. Fourth Edition. Pp 164-166 and 963-964.

Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

(1995-2004). Minerals and Electrolytes. The Merck Manual of Medical Information – Second Home Edition [On-line information]. Available online at http://www.merck.com/mmhe/sec12/ch155/ch155a.html?qt=electrolytes&alt=sh through http://www.merck.com.

Ben-Joseph, E., Reviewed (2004 July). Dehydration. Familydoctor.org Information for Parents [On-line information]. Available online at http://www.kidshealth.org/PageManager.jsp?dn=familydoctor&lic=44&article_set=21646 through http://www.kidshealth.org.

A.D.A.M. editorial, Updated (2003 October 15). Electrolytes. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002350.htm.

Hurd, R. (Updated April 26, 2007). MedlinePlus Medical Encyclopedia: Serum Chloride. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003485.htm. Accessed July 2008.

Mushnick, R. (Updated October 22, 2007.) MedlinePlus Medical Encyclopedia: Chloride—urine. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003601.htm. Accessed July 2008.

Clarke, W and Dufour D R, Editors (2006). Contemporary Practice in Clinical Chemistry. AACC Press, Washington, DC. Pp 321-322, 326.

Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006. Pp 165-167.

MedlinePlus Medical Encyclopedia: Chloride in diet. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002417.htm. Accessed July 2009.