Summary
Hyperkalemia is an electrolyte imbalance characterized by abnormally high levels of potassium in the serum or plasma. There is no universally accepted definition of hyperkalemia; however, the European Resuscitation Council defines hyperkalemia as a serum potassium (K+) level ≥5.5 mEq/L (≥5.5 mmol/L).[1] Hyperkalemia is generally further classified by severity as mild (5.5 to 5.9 mEq/L [5.5 to 5.9 mmol/L]), moderate (6.0 to 6.4 mEq/L [6.0 to 6.4 mmol/L]), or severe (≥6.5 mEq/L [≥6.5 mmol/L]).[1][2][3] However, Kidney Disease: Improving Global Outcomes (KDIGO) guidelines include ECG changes when categorizing severity; on the KDIGO scale, a serum potassium level of 6.0 to 6.4 mEq/L (6.0 to 6.4 mmol/L) with ECG changes is classed as severe.[4] Small changes in serum potassium values can have significant muscular and cardiac effects when severe hyperkalemia is present.
Hyperkalemia is most commonly due either to high intake of potassium in the setting of decreased renal excretion or to extracellular redistribution of potassium from intracellular locations. There is a limited correlation between an elevated serum potassium value and an excess in total body potassium stores. Clinical manifestations of hyperkalemia are uncommon with values <6.0 mEq/L (<6.0 mmol/L).
Hyperkalemia typically presents with no symptoms or with nonspecific features only.[2][3] However, be aware that some patients with severe hyperkalemia may present with cardiac arrest. See Cardiac arrest.
Common acute manifestations of moderate-to-severe hyperkalemia include muscle weakness and ECG changes, with the latter having the potential to progress to a life-threatening arrhythmia.[5] Moderate-to-severe hyperkalemia represents a medical emergency, and an ECG should be obtained to establish whether cardiotoxicity is present. Continuous ECG monitoring should occur until serum potassium values have been brought into a safe range and cardiotoxicity has resolved.
Whereas the treatment of moderate-to-severe hyperkalemia is pre-emptive in the patient without electrocardiographic change, in the presence of electrocardiographic change moderate-to-severe hyperkalemia represents a true medical emergency and requires rapid implementation of measures to reduce serum potassium concentration.[Figure caption and citation for the preceding image starts]: ECG changes in patients with hyperkalemiaBMJ 2009; 339:b4114. Copyright ©2009 by the BMJ Publishing Group [Citation ends].
Differentials
Common
- Chronic kidney disease
- Diabetic ketoacidosis/hyperosmolar hyperglycemic state
- Drug-related decreased cellular entry or increased cellular exit of potassium
- Potassium supplementation with underlying renal dysfunction
- Drug-related reduced urinary potassium excretion
Uncommon
- Acute kidney injury
- Renal tubular acidosis
- Metabolic acidosis
- Congenital adrenal hyperplasia
- Primary adrenal insufficiency (Addison disease)
- Pseudohypoaldosteronism
- Hyperkalemic periodic paralysis
- Tumor lysis syndrome
- Rhabdomyolysis
- Pseudohyperkalemia
- Ureterojejunostomy
Contributors
Authors
Sri G. Yarlagadda, MD
Professor
Kidney Institute
The University of Kansas Medical Center
Kansas City, KS
Disclosures
SGY declares that she has no competing interests.
Acknowledgements
Dr Sri G. Yarlagadda would like to gratefully acknowledge Dr Domenic Sica, a previous contributor to this topic. DS declares that he has no competing interests.
Peer reviewers
Manish Suneja, MD
Assistant Professor
Department of Internal Medicine
Division of Nephrology
University of Iowa Hospital and Clinics
Iowa City, IA
Disclosures
MS declares that he has no competing interests.
Raj Thuraisingham, MBBS, MRCP, FRCP, MD
Consultant Nephrologist
Royal London Hospital
London
UK
Disclosures
RT declares that he has no competing interests.
Peer reviewer acknowledgements
BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.
Disclosures
Peer reviewer affiliations and disclosures pertain to the time of the review.
References
Key articles
Lott C, Karageorgos V, Abelairas-Gomez C, et al. European Resuscitation Council guidelines 2025 special circumstances in resuscitation. Resuscitation. 2025 Oct;215 suppl 1:110753.Full text Abstract
Rafique Z, Peacock F, Armstead T, et al. Hyperkalemia management in the emergency department: an expert panel consensus. J Am Coll Emerg Physicians Open. 2021 Oct 1;2(5):e12572.Full text Abstract
Rossignol P, Legrand M, Kosiborod M, et al. Emergency management of severe hyperkalemia: guideline for best practice and opportunities for the future. Pharmacol Res. 2016 Nov;113(pt a):585-91. Abstract
Deakin C, Clarke AB, Boulton A, et al. Special circumstances guidelines. Oct 2025 [internet publication].Full text
Drennan IR, Berg KM, Böttiger BW, et al. Advanced life support: 2025 International Liaison Committee on Resuscitation consensus on science with treatment recommendations. Circulation. 2025 Oct 21;152(16_suppl_1):S72-115.Full text Abstract
Reference articles
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