Dr. med. Dirk Manski

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Potassium (Kalium) Serum Blood Test

Potassium is the most important intracellular electrolyte (cation). It is involved in numerous physiological processes in the cell and at the cell membrane (membrane potential or transport processes).

Standard value:

3.5–5 mmol/l

Laboratory test method:

Measurement with ion-selective electrode or flame photometer.


Measurement of potassium in serum is indicated in disorders of fluid, electrolyte and acid-base homeostasis.

Differential Diagnosis of Hypokalemia:

Hypokalemia is a low concentration of potassium in the blood. Mild hypokalemia causes no complaints. Severe hypokalemia (<2.5 mmol/l) leads to weakness, constipation and cardiac arrhythmia:

Insufficient intake:

Starvation, wrong dosage in parenteral nutrition.

Renal loss:

Chronic interstitial nephritis, tubulopathies, polyuria after acute renal failure, diuretics, primary or secondary hyperaldosteronism (renal artery stenosis, heart failure, liver cirrhosis, nephrotic syndrome), Cushing syndrome, steroid therapy.

Enteral loss:

Chronic diarrhea, chronic vomiting, nasogastric tube, loss of secretion by enteral fistulas, laxative abuse, treatment with cation exchangers.

Potassium shift from extracellular to intracellular space:

Metabolic alkalosis, treatment of coma diabeticum, treatment of pernicious anemia with vitamin B12, familial hypokalemic paroxysmal paralysis.

Differential Diagnosis of Hyperkalemia:

Hyperkalemia is a high concentration of potassium in the blood. Severe hyperkalemia (>6.5 mmol/l) leads to ECG findings such as peaked T waves, widening of the QRS complex and malignant ventricular arrhythmia.


Overdose of potassium medication, treatment with penicillin, potassium-sparing diuretics, spironolactone or transfusions.

Insufficient renal elimination:

Acute renal insufficiency with oligoanuria, terminal renal insufficiency, adrenal insufficiency.

Potassium shift from intracellular to extracellular space:

Acidosis, severe hemolysis, crush syndrome, chemotherapy (tumor lysis syndrome).

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Guder, W. G. & Nolte, J. Das Laborbuch für Klinik und Praxis
Urban + Fischer, 2009

Siegenthaler 1988 SIEGENTHALER, W. ; SIEGENTHALER, W. (Hrsg.): Differentialdiagnose innerer Krankheiten.
Georg Thieme Verlag, Stuttgart, New York., 1988

  Deutsche Version: Elektrolyte im Serum: Kalium