Differential Diagnosis

An artifactually high value can occur with hemolysis of red blood cells (RBCs) during venipuncture, especially if there is prolonged tourniquet use and fist clenching during the drawing of the blood or at any time prior to potassium measurement.

An artifactually high potassium value can also occur when there are greater than 1,000,000 /µL platelets or greater than 100,000/µL white blood cells (WBCs).

Renal failure from any cause, with oliguria, or as chronic nonoliguric renal failure.

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Excess potassium supplements, potassium-rich foods, salt substitutes, intravenous (IV) potassium, or infusion of potassium-containing drugs, such as potassium penicillin.

Hypoaldosteronism from Addison’s disease or hypofunction of the renin-angiotensin-aldosterone system.

Acute acidosis from diabetic ketoacidosis or from lactic acidosis as found with extensive crush injury, burns, or tissue necrosis.

Ingestion of drugs that inhibit potassium secretion by the kidney.

Dangerous Situations

All of these situations are especially dangerous if the potassium becomes extremely elevated.

Values greater than 7.5 mEq/L are associated with serious cardiac conduction abnormalities.

Commonly Encountered Situations

Hyperkalemia is found frequently in renal failure.

The most common cause of an artifactually elevated potassium is hemolysis of RBCs.

Suggested Additional Lab Testing

Determine whether the serum or plasma showed evidence of hemolysis by a change in color from yellow to pink or red.

Complete blood count (CBC) to assess platelet count and WBC count.

Evidence of renal disease from an elevated creatinine or blood urea nitrogen (BUN), or decreased urine output.

Serum aldosterone to assess for hypoaldosteronism.

Blood gases to evaluate possible acidosis.