MLT GlobeBicarbonate (total CO₂)
Electrolytes · also called HCO₃⁻, TCO2, CO2 content
What it measures
Serum total CO₂ is almost entirely bicarbonate and reflects the metabolic side of acid–base balance. It is part of the routine electrolyte panel and is used to detect metabolic acidosis or alkalosis.
Specimen and preparation
- Specimen: Serum or lithium-heparin plasma
- Tube: Gold top
- Preparation: Fill tubes adequately and keep capped; exposure to air lowers the result.
Reference range
| Group | Range |
|---|---|
| Adult | 22–29 mmol/L |
Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.
Causes of high values
- Vomiting and gastric loss
- Diuretics
- Compensation for chronic respiratory acidosis
- Hyperaldosteronism
- Alkali ingestion
Causes of low values
- Diabetic ketoacidosis and lactic acidosis
- Kidney failure
- Diarrhoea
- Renal tubular acidosis
- Underfilled tube (artefact)
Method
Enzymatic (PEP carboxylase) or ISE-based CO₂ electrode
Good to know
Confirm the acid–base disorder with arterial or venous blood gas analysis.
Related tests
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