What does the Potassium, Serum test measure?

Why is Potassium, Serum measured?

In the CMP context, serum potassium is interpreted alongside sodium, bicarbonate, and creatinine/eGFR — the electrolyte-acid-base-renal pattern providing integrated physiological context. Hypokalaemia alongside metabolic alkalosis (elevated bicarbonate) suggests vomiting or diuretic use. Hyperkalaemia alongside metabolic acidosis (low bicarbonate) and elevated creatinine is consistent with CKD with impaired potassium excretion and retained acids. Hypokalaemia alongside elevated sodium and hypertension is the classic pattern of primary aldosteronism. Haemolysis must always be excluded before treating elevated potassium.

Reference ranges

Standard reference

3.5–5.1 mEq/L (3.5–5.1 mmol/L) # REVIEWER FLAG: Confirm Quest Diagnostics potassium reference range — upper limit is 5.0 mEq/L on some platforms. Confirm critical value thresholds (<2.5 mEq/L and ≥6.0–6.5 mEq/L) and whether Quest includes a haemolysis index flagging on potassium results.

Functional medicine optimal

3.8–4.5 mEq/L (functional medicine cardiovascular optimal — lowest arrhythmia and mortality risk in population data). # REVIEWER FLAG: Not a formal clinical treatment threshold — reviewer to confirm framing.

Units

mEq/L, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.