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Electrolytes & Minerals

Potassium (K⁺)

Normal range 3.5–5 mEq/L (3.5–5 mmol/L SI). Specimen: Serum or plasma.

Also known as: serum potassium, k.

3.5–5 mEq/LCritical: read below

Reference range

ConventionalmEq/L
3.55
SImmol/L
3.55
SpecimenSerum or plasma
Conventional range3.5–5 mEq/L
SI range3.5–5 mmol/L
Conversion factor×1 (conventional → SI)
Critical value< 2.5 or > 6.5 mmol/L (life-threatening arrhythmia risk)
PanelElectrolytes & Minerals

Convert any Potassium (K⁺) result between units on the unit converter.

What is the normal range for Potassium (K⁺)?

The standard teaching reference range for Potassium (K⁺) is 3.5–5 mEq/L in conventional units, or 3.5–5 mmol/L in SI units. This value is measured in serum or plasma.

A commonly taught critical (panic) value is < 2.5 or > 6.5 mmol/L (life-threatening arrhythmia risk). Critical results are reported to the provider immediately under your facility's policy.

Source: Adult reference values compiled from Pagana & Pagana, Mosby's Diagnostic and Laboratory Test Reference, and Fischbach & Dunning, A Manual of Laboratory and Diagnostic Tests. Reference ranges vary by laboratory, method, age, sex, and population — always use the range printed on the actual result.

Above the range

Common causes of a high Potassium (K⁺)

  • Kidney failure
  • Acidosis
  • Potassium-sparing diuretics / ACE inhibitors
  • Cell lysis (hemolysis, rhabdomyolysis)

Below the range

Common causes of a low Potassium (K⁺)

  • Diuretics
  • Vomiting or diarrhea (GI loss)
  • Alkalosis
  • Insulin or beta-agonist therapy

At the bedside

Nursing considerations

  • Place on cardiac monitoring at critical levels; watch for peaked or flattened T waves.
  • Never give IV potassium by push — always dilute and infuse per protocol.
  • A hemolyzed specimen falsely elevates potassium; redraw if suspected.

Study aid

Your notes on Potassium (K⁺)

Same panel

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Anion Gap8–16 mEq/LBicarbonate (CO₂ content)22–29 mEq/LCalcium, Ionized4.6–5.3 mg/dLCalcium, Total (Ca²⁺)8.6–10.2 mg/dLChloride (Cl⁻)98–106 mEq/LMagnesium (Mg²⁺)1.6–2.6 mg/dL