What is this test?
Sodium is the main electrolyte in fluid outside cells and helps regulate water balance, nerves and muscles. The blood concentration reflects water balance as much as total body sodium.
Why might it be ordered?
- To investigate dehydration, swelling, confusion, weakness or an acute illness.
- To monitor kidney, heart or hormone conditions and medicines such as diuretics.
What sample is needed?
A blood sample is required. The laboratory chooses the correct tube and handles the sample for this test.
How should you prepare?
Ask the laboratory whether you need to fast or attend at a particular time. Do not stop or change medicines or supplements unless your clinician tells you to.
How should you understand the result?
A high or low sodium value can be medically important, especially with neurological symptoms. The cause is assessed with fluid status, glucose, kidney function and sometimes urine tests.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.