Chemical Pathology


Potassium forms part of the standard U&E profile but can also be assayed in urine.

Sample requirements

For adults, blood taken into a 5mL gold top gel tube (or rust top for the Acute Unit)

5ml gold tube

For children, blood taken into a 3.5mL rust top gel tube

3.5ml rust top tube

For neonates, blood taken into a 0.8mL minicollect lithium heparin tube. Please list the tests of particular interest so that some priority can be given to analysis if plasma volumes are small.

Minicollect lithium heparin tube

For 24 hour urine potassium, collect urine into a 3L brown bottle:-

24-hour urine container

For random urine potassium, send urine in a plain white narrow tube

6ml plain urine tube


Do not store blood samples. Send as soon as possible at ambient temperature, to the laboratory (maximum of 8 hours). If clinically acceptable, urine samples can be stored refrigerated overnight if necessary.

Required information

Relevant clinical details including medication e.g. ACE inhibitors, fluid replacement.

For 24 hour urine collections, please indicate clearly start and finish dates and times.

The labelling of the request form and the sample must conform to the Policy for Specimen and Request Form Labelling for Pathology Users

Turnaround times

The assays are run throughout the day and night.

The in-lab turnaround time is normally less than 24 hours.

The test can be ordered as an urgent request.

Reference ranges

Serum potassium 3.5 - 5.3 mmol/L

Adult 24 hour urine potassium 25 - 125 mmol/24h

Further information

To learn more about potassium visit Lab Tests Online or access the potassium monograph of the Association for Clinical Biochemistry and Laboratory Medicine

Monograph of the Association for Clinical biochemistry and Laboratory Medicine