Preferred Sample Type

Potassium (serum)

Suitable Specimen Types

  • Serum
  • Li Hep Plasma
1.0 mL blood (paediatric minimum volume 30 uL serum)

Sample Processing in Laboratory


Sample Preparation

Centrifuge - do not leave on cells overnight

Turnaround Time

1 day

Sample Stability

4°C once centrifuged

Potassium (serum)

General Information

Potassium is the main intracellular cation. Small changes in the distribution of potassium can give rise to medical emergencies. The serum and urine concentrations of potassium reflect a complex interplay of hormonal and other systems that regulate the intracellular content. The main regulators of potassium concentrations in serum and urine are, insulin, aldosterone, catecholamines and acid base status. Diseases of the kidney, adrenal and any process that affects acid base disturbance will affect plasma potassium concentration. Crush injuries are also a cause of hyperkalaemia.

High potassium concentrations can give rise to a medical emergency requiring rapid intervention. Changes in potassium concentration affect the electrical conductivity of muscles and cardiac muscle and in high concentrations can cause cardiac arrest.

Patient Preparation



Samples left on cells and haemolysed samples will not be analysed

Potassium can be artificially elevated by delayed centrifugation of samples. Interpret a raised potassium with caution if there has been a  >6 hr delay between the sample being taken and received by the laboratory.

Exposure of whole blood to extremes of temperature affects potassium concetration. High temperatures lead to falsely low potassium results and low temperatures lead to falsely high results.

Note: Insulin, corticosteroids, furosemide, thiazides can decrease potassium. Potassium sparing diurectics, ACE inhibitors can increase potassium.

Reference Range

Adult    3.5-5.3 mmol/L

Plasma Potassium Paediatrics

Neonates (<4weeks)   3.4-6.0 mmol/L

Infant (<1yr)   3.5-5.7 mmol/L

1-16yrs          3.5-5.0 mmol/L

(Source : Pathology Harmony Recommendations)


  • EQA Scheme?: Yes
  • EQA Status:


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The Trust Laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital were awarded UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard in May 2015. For a list of accredited tests and other information please visit the test database
Tests not appearing on this scope are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235