Electrolytes & Minerals

Potassium (K⁺)

Q: What causes a high Potassium (K⁺)?

Common causes of a high Potassium (K⁺): Kidney failure; Acidosis; Potassium-sparing diuretics / ACE inhibitors; Cell lysis (hemolysis, rhabdomyolysis).

Q: What causes a low Potassium (K⁺)?

Common causes of a low Potassium (K⁺): Diuretics; Vomiting or diarrhea (GI loss); Alkalosis; Insulin or beta-agonist therapy.

Q: What is a critical Potassium (K⁺) value?

For Potassium (K⁺), the commonly taught critical (panic) value is: 6.5 mmol/L (life-threatening arrhythmia risk). Critical results are reported to the provider immediately under your facility's policy.

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 value: read below

Reference range

ConventionalmEq/L

3.55

SImmol/L

3.55

Combined adult band. LabVals does not publish separate men's, women's, or pediatric ranges for Potassium (K⁺); those can be narrower than the band shown.

Potassium (K⁺) reference range, specimen, and conversion details
Specimen	Serum or plasma
Conventional range	3.5-5 mEq/L
SI range	3.5-5 mmol/L
Conversion factor	×1 (conventional → SI)
Critical value	< 2.5 or > 6.5 mmol/L (life-threatening arrhythmia risk)
Panel	Electrolytes & 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.

What is a critical Potassium (K⁺) value?

For Potassium (K⁺), the 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

What causes a high Potassium (K⁺)?

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

What causes a high Potassium (K⁺)? Read as its own page

Below the range

What causes a low Potassium (K⁺)?

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

What causes a low Potassium (K⁺)? Read as its own page

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.

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