Hypokalemia: Difference between revisions
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==Background==
==Background==
*Serum potassium <3.5 mEq/L
*Most common electrolyte abnormality encountered in clinical practice
*Severity:
**Mild: 3.0-3.5 mEq/L
**Moderate: 2.5-3.0 mEq/L
**Severe: <2.5 mEq/L (risk of arrhythmia, respiratory failure)
*Every 1 mEq/L decrease in serum K represents ~200-400 mEq total body deficit
===Causes===
*Decreased intake: malnutrition, anorexia, alcoholism
*GI losses (most common):
**Vomiting (metabolic alkalosis → renal K wasting)
**Diarrhea (direct K loss)
**NG suction, laxative abuse
*Renal losses:
**Diuretics (loops, thiazides — most common medication cause)
**Hyperaldosteronism (primary or secondary)
**[[Renal tubular acidosis]] (types 1 and 2)
**Hypomagnesemia (impairs renal K conservation)
**Osmotic diuresis ([[DKA]])
*Transcellular shift (K moves into cells):
**Insulin (therapeutic or endogenous)
**Beta-2 agonists (albuterol)
**Alkalosis
**Catecholamine surge, thyrotoxicosis
**Hypothermia (shifts K intracellularly)


==Clinical Features==
==Clinical Features==
*Central nervous system
*Often asymptomatic with mild hypokalemia
**[[Weakness]]
*Muscle weakness (proximal > distal), cramps, myalgia
**[[myalgia|Cramps]]
*Ileus, constipation, nausea/vomiting
**Hyporeflexia
*Rhabdomyolysis (severe hypokalemia)
*Gastrointestinal
*Cardiac arrhythmias:
**[[Ileus]]
**PACs, PVCs → atrial or ventricular [[tachycardia]] → torsades de pointes → VF
*Renal
**Potentiates [[digoxin toxicity]]
**[[Metabolic alkalosis]]
*Cardiovascular
**[[PACs]]/[[PVCs]]
**[[ACLS: Bradycardia|Bradycardia]] or [[atrial tachycardia|atrial]]/[[junctional tachycardia]]
**[[AV block]]
**[[Tachycardia (wide)|Ventricular tachycardia]], [[Adult pulseless arrest|Ventricular fibrillation]]


==Differential Diagnosis<ref>In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. McGraw-Hill; Accessed November 29, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109381281</ref>==
===ECG Changes===
[[File:Hypokalemia.png|thumb|Differential diagnosis of hypokalemia]]
*Flattened T waves (earliest)
===Intracellular Shift===
*Prominent U waves (after T wave)
*Alkalosis (each 0.10 rise in pH causes 0.5 decrease)
*ST depression
*[[Insulin]]
*Prolonged QT interval
*[[Beta agonists]]
*T-U fusion (severe)
*[[Hypokalemic periodic paralysis]]


===Decreased intake===
==Differential Diagnosis==
*Special diets or those low in potassium
*Medication-induced (diuretics, insulin, albuterol)
*Chronic [[alcohol Abuse|alcohol abuse]]
*GI losses (vomiting, diarrhea)
*Fasting
*[[Diabetic ketoacidosis]] (total body K depleted despite possible normal level)
*Eating disorders
*Hyperaldosteronism
*[[Renal tubular acidosis]]
*Hypomagnesemia
*Bartter/Gitelman syndrome
*Thyrotoxic periodic paralysis


===Increased loss===
==Evaluation==
*GI
*ECG (look for U waves, flattened T waves, prolonged QT)
**[[Vomiting]], [[diarrhea]], fistula
*BMP: K level, bicarbonate (alkalosis?), glucose, creatinine
*Renal
*Magnesium level (hypokalemia refractory to replacement if Mg not corrected)
**[[Diuretics]]
*Calcium level (concurrent abnormalities)
**Osmotic diuresis (late-presenting [[Diabetic ketoacidosis|DKA]])
*Consider: urine K (spot urine K/Cr ratio or 24h K), urine chloride, TSH, cortisol/aldosterone if unexplained
**Hyperaldosteronism
*Digoxin level if on digoxin (hypokalemia increases digoxin sensitivity)
**[[Hypercalcemia]]
**[[Hypomagnesemia]]
*Increased sweat loss
**Heavy exercise
**Heat stroke
**Fever


===Drugs===
==Management==
*[[Penicillins]]
===Guiding Principles===
*[[Lithium toxicity|Lithium]]
*Always check and replace magnesium first — hypokalemia is refractory to correction with concurrent hypomagnesemia
*L-dopa
*Oral replacement preferred when possible (better tolerated, less risky)
*[[Theophylline]], methylxanthines (e.g. [[caffeine]]
*IV replacement for severe hypokalemia, ECG changes, or NPO patients
*[[Insulin]]
*Barium
*[[Quinine]]
*Catecholamines


===Other===
===Mild Hypokalemia (3.0-3.5 mEq/L)===
*Acute leukemia and lymphomas
*Oral KCl 20-40 mEq PO q2-4h (typical total dose 40-100 mEq/day)
*Recovery from megaloblastic anemia
*Increase dietary potassium
*Hypothermia (accidental or induced)


==Evaluation==
===Moderate Hypokalemia (2.5-3.0 mEq/L)===
*Serum potassium level is diagnostic
*KCl 10-20 mEq/hr IV via peripheral line (max 40 mEq/L concentration peripherally)
**Normal = 3.5-5meq/L
**Higher concentrations require central line
**Severe hypokalemia = <2.5meq/L
*Max infusion rate: 10-20 mEq/hr (peripheral); up to 40 mEq/hr via central line with cardiac monitoring
*Always check magnesium
*Concurrent oral supplementation
**Na+/K+ ATPase pump requires Mg to function, therefore low Mg can lead to refractory hypoK
*Suggestive [[ECG]] findings:  
**[[ST segment depression]]
**U wave (V4-V6)  
**[[QT prolongation]]
**[[Premature ventricular contraction]]


[[Image:ECG Hypokalemia.jpg]]
===Severe Hypokalemia (<2.5 mEq/L or ECG Changes)===
*Continuous cardiac monitoring
*KCl 20-40 mEq/hr IV via central line
*Magnesium sulfate 2g IV (if Mg not checked yet, give empirically)
*Recheck K every 1-2 hours
*May require 200+ mEq total replacement


==Management==
===Special Situations===
*Potassium repletion (PO or IV)
*[[DKA]]: K may be normal or elevated on presentation but total body stores are depleted
**Every 10mEq KCl → serum K ↑ ~0.1mEq/L
**Replace K ''before or concurrent with insulin'' when K <5.3
**PO preferred (if symptomatic or level is <2.5, both oral and IV should be given)
**'''Do NOT start insulin if K <3.3''' — replace K to >3.3 first
*Oral potassium
*[[Digoxin toxicity]]: maintain K >4.0 mEq/L
**Inexpensive and rapidly absorbed
*Refractory hypokalemia: check and replace magnesium<ref>Huang CL, Kuo E. Mechanism of hypokalemia in magnesium deficiency. J Am Soc Nephrol. 2007;18(10):2649-2652. PMID 17804670</ref>; consider amiloride or spironolactone
**KCl tablet (elixir form available but has poor taste)
**K-Dur (extended release tablet) is large and may be difficult to swallow
**If sending patient home can also increase food intake of potassium as an alternative or supplementing potassium tablets. Printable table that can be given to the patient available at this reference: <ref>[https://www.mayoclinic.org/drugs-supplements/potassium-supplement-oral-route-parenteral-route/description/drg-20070753?p=1 Potassium Supplement (Oral Route, Parenteral Route) from Mayo Clinic]</ref>.
*Intravenous potassium
**Must be given in dilute solutions at slow rate (10meq/hour) to minimize side effects and cardiac toxicity
**Generally should not give more than 40mEq via IV
**Side effects: Local tissue burning, phlebitis, sclerosis
*Also treat [[Hypomagnesemia]] if present
*Re-check ECG after treatment <ref>Slovis, Corey. "Electrolyte Emergencies". Presentation.</ref>
*Hypokalemia in acute or recent [[myocardial infarction]] places patients at much higher risk for [[ventricular fibrillation]]<ref>Goyal A et al. Serum Potassium Levels and Mortality in Acute Myocardial Infarction. JAMA. 2012;307(2):157-164.</ref>
**Previous studies and many professional organizations recommend maintaining K between 4.0 - 5.0 mEq/L in MI patients
**However, more recent studies suggest 3.5 - 4.5 mEq/L results in the lowest mortality


==Disposition==
==Disposition==
*Based on underlying cause
*Admit if K <2.5, symptomatic, ECG changes, arrhythmia, or ongoing losses
*One admission criteria is potassium less than 3.0 meq/L and a QTc that is close to or more than 500 msec. <ref>[https://www.emrap.org/episode/emrap2018august/electrolyte EM:RAP 2018 August Electrolyte Emergencies - Part 1 - All Things Potassium]</ref>
*Continuous telemetry for K <3.0 or ECG changes
*Discharge if mild (3.0-3.5), asymptomatic, clear correctable cause, tolerated PO replacement, normal ECG
*Close follow-up with recheck in 24-48 hours


==See Also==
==See Also==
*[[Electrolyte Abnormalities (Main)]]
*[[Hypokalemic periodic paralysis]]
*[[Hyperkalemia]]
*[[Hyperkalemia]]
*[[Hypomagnesemia]]
*[[Digoxin toxicity]]
*[[Diabetic ketoacidosis]]
*[[Electrolyte imbalances]]


==External Links==
==References==
*[https://emcrit.org/ibcc/hypokalemia/ IBCC Hypokalemia]
*Kardalas E, et al. Hypokalemia: a clinical update. ''Endocr Connect''. 2018;7(4):R135-R146. PMID 29540487
*[http://ddxof.com/electrolyte-abnormalities/ DDxOf: Differential Diagnosis of Electrolyte Abnormalities]
*Gennari FJ. Hypokalemia. ''N Engl J Med''. 1998;339(7):451-458. PMID 9700180
*Viera AJ, Wouk N. Potassium disorders: hypokalemia and hyperkalemia. ''Am Fam Physician''. 2015;92(6):487-495. PMID 26371733
*Crop MJ, et al. Role of magnesium in hypokalemia. ''Crit Care''. 2012;16(1):229. PMID 22866973


==References==
[[Category:Renal]]
<references/>
[[Category:Critical Care]]
[[Category:FEN]]

Latest revision as of 10:06, 22 March 2026

Background

  • Serum potassium <3.5 mEq/L
  • Most common electrolyte abnormality encountered in clinical practice
  • Severity:
    • Mild: 3.0-3.5 mEq/L
    • Moderate: 2.5-3.0 mEq/L
    • Severe: <2.5 mEq/L (risk of arrhythmia, respiratory failure)
  • Every 1 mEq/L decrease in serum K represents ~200-400 mEq total body deficit

Causes

  • Decreased intake: malnutrition, anorexia, alcoholism
  • GI losses (most common):
    • Vomiting (metabolic alkalosis → renal K wasting)
    • Diarrhea (direct K loss)
    • NG suction, laxative abuse
  • Renal losses:
    • Diuretics (loops, thiazides — most common medication cause)
    • Hyperaldosteronism (primary or secondary)
    • Renal tubular acidosis (types 1 and 2)
    • Hypomagnesemia (impairs renal K conservation)
    • Osmotic diuresis (DKA)
  • Transcellular shift (K moves into cells):
    • Insulin (therapeutic or endogenous)
    • Beta-2 agonists (albuterol)
    • Alkalosis
    • Catecholamine surge, thyrotoxicosis
    • Hypothermia (shifts K intracellularly)

Clinical Features

  • Often asymptomatic with mild hypokalemia
  • Muscle weakness (proximal > distal), cramps, myalgia
  • Ileus, constipation, nausea/vomiting
  • Rhabdomyolysis (severe hypokalemia)
  • Cardiac arrhythmias:

ECG Changes

  • Flattened T waves (earliest)
  • Prominent U waves (after T wave)
  • ST depression
  • Prolonged QT interval
  • T-U fusion (severe)

Differential Diagnosis

  • Medication-induced (diuretics, insulin, albuterol)
  • GI losses (vomiting, diarrhea)
  • Diabetic ketoacidosis (total body K depleted despite possible normal level)
  • Hyperaldosteronism
  • Renal tubular acidosis
  • Hypomagnesemia
  • Bartter/Gitelman syndrome
  • Thyrotoxic periodic paralysis

Evaluation

  • ECG (look for U waves, flattened T waves, prolonged QT)
  • BMP: K level, bicarbonate (alkalosis?), glucose, creatinine
  • Magnesium level (hypokalemia refractory to replacement if Mg not corrected)
  • Calcium level (concurrent abnormalities)
  • Consider: urine K (spot urine K/Cr ratio or 24h K), urine chloride, TSH, cortisol/aldosterone if unexplained
  • Digoxin level if on digoxin (hypokalemia increases digoxin sensitivity)

Management

Guiding Principles

  • Always check and replace magnesium first — hypokalemia is refractory to correction with concurrent hypomagnesemia
  • Oral replacement preferred when possible (better tolerated, less risky)
  • IV replacement for severe hypokalemia, ECG changes, or NPO patients

Mild Hypokalemia (3.0-3.5 mEq/L)

  • Oral KCl 20-40 mEq PO q2-4h (typical total dose 40-100 mEq/day)
  • Increase dietary potassium

Moderate Hypokalemia (2.5-3.0 mEq/L)

  • KCl 10-20 mEq/hr IV via peripheral line (max 40 mEq/L concentration peripherally)
    • Higher concentrations require central line
  • Max infusion rate: 10-20 mEq/hr (peripheral); up to 40 mEq/hr via central line with cardiac monitoring
  • Concurrent oral supplementation

Severe Hypokalemia (<2.5 mEq/L or ECG Changes)

  • Continuous cardiac monitoring
  • KCl 20-40 mEq/hr IV via central line
  • Magnesium sulfate 2g IV (if Mg not checked yet, give empirically)
  • Recheck K every 1-2 hours
  • May require 200+ mEq total replacement

Special Situations

  • DKA: K may be normal or elevated on presentation but total body stores are depleted
    • Replace K before or concurrent with insulin when K <5.3
    • Do NOT start insulin if K <3.3 — replace K to >3.3 first
  • Digoxin toxicity: maintain K >4.0 mEq/L
  • Refractory hypokalemia: check and replace magnesium[1]; consider amiloride or spironolactone

Disposition

  • Admit if K <2.5, symptomatic, ECG changes, arrhythmia, or ongoing losses
  • Continuous telemetry for K <3.0 or ECG changes
  • Discharge if mild (3.0-3.5), asymptomatic, clear correctable cause, tolerated PO replacement, normal ECG
  • Close follow-up with recheck in 24-48 hours

See Also

References

  • Kardalas E, et al. Hypokalemia: a clinical update. Endocr Connect. 2018;7(4):R135-R146. PMID 29540487
  • Gennari FJ. Hypokalemia. N Engl J Med. 1998;339(7):451-458. PMID 9700180
  • Viera AJ, Wouk N. Potassium disorders: hypokalemia and hyperkalemia. Am Fam Physician. 2015;92(6):487-495. PMID 26371733
  • Crop MJ, et al. Role of magnesium in hypokalemia. Crit Care. 2012;16(1):229. PMID 22866973
  1. ↑ Huang CL, Kuo E. Mechanism of hypokalemia in magnesium deficiency. J Am Soc Nephrol. 2007;18(10):2649-2652. PMID 17804670
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