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Test Code CO2 Carbon Dioxide, Plasma

Specimen Type

Preferred: Plasma

Acceptable: Serum


Preferred: Li Heparin (Mint Green or Dark Green)

Acceptable: Serum Red Top tube or Gold SST

Preferred Volume

3 mL

Offsite Collection Instructions

The tube must be remain capped to prevent exposure to air.

UCMC Collection Instructions

 The tube must be remain capped to prevent exposure to air.  Once per admit.  If serial monitoring needed, Q daily.



Turnaround Time

4 hours

STAT Availability


Test Usage

The bicarbonate content of serum or plasma is a significant indicator of electrolyte dispersion and anion deficit.

Test Methodology

Spectrophotometric, enzymatic endpoint

CPT Code


Test Includes

Bicarbonate (HCO3-) in plasma

STAT Turnaround Time

1 hour

Reference Range

23 – 30 mEq/L

Critical Results

<10 mEq/L; >40 mEq/L

Test Limitations

Bicarbonate content in uncapped tubes decreases by approximately 4 mEq/L after one hour

Minimum Volume

2 mL

Fee Code



CO2, bicarbonate