Lapis ISSN 2398-2969

Blood biochemistry: sodium

Synonym(s): Na

Contributor(s): Anna Meredith, Vetstream Ltd, Michael Waters, John Chitty


  • Present mainly in extracellular fluid but freely diffusible throughout ECF.
  • Usually base excess in diet so dietary alterations unlikely to affect concentrations in body.
  • Regulated by kidneys and important in regulation of fluid balance.
  • Sodium and chloride Blood biochemistry: chloride ions are the most osmotically active solute in plasma.
  • Measured in conjunction with other electrolytes, eg chloride Blood biochemistry: chloride and potassium Blood biochemistry: potassium where metabolic disturbances may be suspected, eg diarrhea. Always assess in association with osmolality where pseudohyponatremia (isotonic/hypertonic) is not significant, whereas true hyponatremia (hypotonic) is significant.
  • In combination with urine electrolyte concentrations for fractional electrolyte excretion in assessment of renal failure.


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  • Widely available at commercial laboratories.

Technique (intrinsic) limitations

  • Test results only significant in conjunction with other laboratory results and clinical findings.

Result Data

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Benson K G & Paul-Murphy J (1999) Clinical pathology of the domestic rabbit: acquisition and interpretation of samples. Vet Clin North Am Exotic Anim Pract 2 (3), 539-552 PubMed.
  • Ardiaca M, Bonhevi C, & Montesinos A (2013) Point of care blood gas and electrolyte analysis in rabbits. Vet Clin North Am Exotic Anim Pract 16 (1), 175- 196.

Other sources of information

  • Saunders R A & Rees Davies R (2005) Notes on Rabbit Internal Medicine. Blackwells, Oxford, UK.
  • Varga M (2014) Textbook of Rabbit Medicine. 2nd edn. Butterworth Heinemann Elsevier, London.
  • Wesche P (2014) Clinical Pathology in BSAVA Manual of Rabbit Medicine. Eds: Meredith A & Lord B. pp 124-137. BSAVA, Gloucester, UK.