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:


The laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital form part of the services provided by University Hospitals Birmingham and are UKAS (United Kingdom Accreditation Service) accredited to the ISO 15189:2012 standard. For a list of accredited tests and other information please visit the UKAS website using the following link:

  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217
  • United Kingdom Health Security Agency laboratory is a UKAS accredited medical laboratory No.8213

Tests not appearing on the UKAS Schedule of Accreditation 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 test information, please visit the test database:

Protection of personal information - Laboratory Medicine comply with the Trust Data Protection policy and have procedures in place to allow the Directorate and its employees to comply with the Data Protection act  1998 and associated best practice and guidance.

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