Base excess arterial


1 mL arterial blood collected anaerobically in a heparinised syringe (sufficient for oxygen, carbon dioxide, pH measurements) and transported rapidly to the laboratory in a capped syringe with needle removed.


Derived parameter from pH, pCO2 and haemoglobin measurements; calculated routinely with blood gas analysis.

Reference Interval:

(-3) to (+3) mmol/L.


Assessment of the metabolic component of acid-base disorders.


Base excess is increased in metabolic alkalosis (primary or secondary to respiratory acidosis) and is decreased in metabolic acidosis (primary or secondary to respiratory alkalosis).


Siggaard-Andersen O. Scand J Clin Lab Invest 1971; 27: 239-245.

Verma AK, Roach P. The interpretation of arterial blood gases. Australian Prescriber 2010: 33: 124-129.