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Hypokalemia in Emergency Medicine

  • Author: David Garth, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
Updated: Oct 29, 2015


Potassium is one of the body's major ions. Nearly 98% of the body's potassium is intracellular. The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential. Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems.[1, 2, 3]

The kidney determines potassium homeostasis, and excess potassium is excreted in the urine.

The reference range for serum potassium level is 3.5-5 mEq/L, with total body potassium stores of approximately 50 mEq/kg (ie, approximately 3500 mEq in a 70-kg person).

Hypokalemia is defined as a potassium level less than 3.5 mEq/L.

Moderate hypokalemia is a serum level of 2.5-3 mEq/L.

Severe hypokalemia is defined as a level less than 2.5 mEq/L.



Hypokalemia may result from conditions as varied as renal or GI losses, inadequate diet, transcellular shift (movement of potassium from serum into cells), and medications.




United States

As many as 20% of hospitalized patients are hypokalemic; however, hypokalemia is clinically significant in only about 4-5% of these patients. Severe hypokalemia is relatively uncommon.

Up to 14% of outpatients who undergo laboratory testing are found to be mildly hypokalemic.

Approximately 80% of patients who are receiving diuretics become hypokalemic.


Incidence is equal in males and females.



Hypokalemia usually resolves with appropriate therapy.


Patient Education

Diet modification is recommended for those patients who are predisposed to hypokalemia. Increase intake of bananas, tomatoes, oranges, and peaches because they are high in potassium.

For patient education resources, see the Endocrine System Center, as well as Low Potassium.

Contributor Information and Disclosures

David Garth, MD Attending Physician, Department of Emergency Medicine, Mary Washington Hospital

David Garth, MD is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Howard A Bessen, MD Professor of Medicine, Department of Emergency Medicine, University of California, Los Angeles, David Geffen School of Medicine; Program Director, Harbor-UCLA Medical Center

Howard A Bessen, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Chief Editor

Romesh Khardori, MD, PhD, FACP Professor of Endocrinology, Director of Training Program, Division of Endocrinology, Diabetes and Metabolism, Strelitz Diabetes and Endocrine Disorders Institute, Department of Internal Medicine, Eastern Virginia Medical School

Romesh Khardori, MD, PhD, FACP is a member of the following medical societies: American Association of Clinical Endocrinologists, American College of Physicians, American Diabetes Association, Endocrine Society

Disclosure: Nothing to disclose.

Additional Contributors

Robin R Hemphill, MD, MPH Associate Professor, Director, Quality and Safety, Department of Emergency Medicine, Emory University School of Medicine

Robin R Hemphill, MD, MPH is a member of the following medical societies: American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.


I would like to thank my wife, Mary. Her patience, love, and reassurance, are my bedrock.

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Prominent U waves after T waves in hypokalemia.
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