Potassium

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Also known as: K
Formal name: Potassium

At a Glance

Why Get Tested?

To determine whether your potassium level is within normal limits and to help evaluate an electrolyte imbalance; to monitor chronic or acute hyperkalemia or hypokalemia

When to Get Tested?

As part of a routine medical exam, when you have symptoms such as weakness and/or cardiac arrhythmia, or when an electrolyte imbalance is suspected; at regular intervals when you are taking a medication and/or have a disease or condition, such as high blood pressure (hypertension) or kidney disease, that can affect your potassium level

Sample Required?

A blood sample drawn from a vein in the arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

This test measures the amount of potassium in the blood. Potassium is an electrolyte that is vital to cell metabolism and muscle function. Potassium, along with other electrolytes such as sodium, chloride, and bicarbonate (total CO2), helps regulate the amount of fluid in the body, stimulates muscle contraction, and maintains a stable acid-base balance. Potassium is present in all body fluids, but most potassium is found within your cells. Only about 2% is present in fluids outside the cells and in the liquid part of the blood (called serum or plasma). Because the blood concentration of potassium is so small, minor changes can have significant consequences. If potassium levels are too low or too high, there can be serious health consequences; a person may be at risk for developing shock, respiratory failure, or heart rhythm disturbances. An abnormal potassium level can alter the function of neuromuscular tissue; for example, the heart muscle may lose its ability to contract.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm.

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

Pagana K, Pagana T. Mosby’s Manual of Diagnostic and Laboratory Tests. 4th edition, Pp 421-424.

MedlinePlus Medical Encylopedia. Potassium test. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003484.htm. Accessed August 2011. 

National Kidney Foundation. Potassium and Your CKD Diet. Available online at http://www.kidney.org/atoz/content/potassium.cfm through http://www.kidney.org. Accessed August 2011. 

Sources Used in Previous Reviews

Hayes, Denise D. When Potassium Takes Dangerous Detours. Nursing 2007 Nov. 56hn1 56hn4.

Bauer, Daniel M.; Ernst, Dennis; Willeford, Susan; Gambino, Raymond. Investigating Elevated Potassium Values. MLO Nov 2006, Pp 24-26.

Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Pp 336-337.

American Heart Association. Potassium. Available online through http://www.americanheart.org. Accessed February 2008.

Pikilidou MI, et al. Blood pressure and serum potassium levels in hypertensive patients receiving or not receiving antihypertensive treatment. Clin Exp Hypertens. 2007 Nov;29(8):563-73. Abstract available online through http://www.ncbi.nlm.nih.gov/pubmed. Accessed February 2008.

Waring WS, Stephen AF, Malkowska AM, Robinson OD. Acute Acetaminophen Overdose Is Associated with Dose-Dependent Hypokalaemia: A Prospective Study of 331 Patients. Basic Clin Pharmacol Toxicol. 2007 Nov 28. Abstract available online through http://www.ncbi.nlm.nih.gov/pubmed. Accessed February 2008.

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

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 through http://www.merck.com.

Ben-Joseph, E., Reviewed (2004 July). Dehydration. Familydoctor.org Information for Parents [On-line information]. Available online 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.