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Alias: Total CO2 TCO2 Carbon Dioxide Content CO2 Content Bicarb HCO3

Discipline: Clinical Chemistry

Test information: Usually as part of a renal profile , to screen for an electrolyte or acid-base imbalance. Also known as total CO . In metabolic acidosis, bicarbonate is reduced, e.g. in diabetic ketoacidosis. In metabolic alkalosis, it is increased . as in pyloric stenosis or the compensated respiratory acidosis of chronic obstructive airways disease.

Specimen Type(s)
  • Blood;
Other Acceptable Specimen Type(s)
Specimen Container - Adult
  • Gold Top SST BD;
Specimen Container - Paediatric
  • Light Green Top Microtainer BD;
  • N/A;
Part of a test profile?
Volume (min) of sample to be sent to laboratory
Patient Preparation, Sample Handling and Transport
Maximum add on time
Units and Reference Ranges / Interpretation
RR for Males and Females
Up to 16 Yrs - 19 - 28 - mmol/L
> 16 yrs - 22 - 29 - mmol/L
UKAS number
UKAS accredited test?
Serum bicarbonate is not a very reliable assay from a clinical point of view, since total CO² is being measured. Arterial blood gas samples provide a more reliable indication of acid/base status.

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Last updated: 03-05-2024