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Test Code CO2 Carbon Dioxide, Serum

Additional Codes

Epic: LAB55

Specimen Required

Specimen Type: Serum

Collection Container/Type

Preferred: Serum gel

Acceptable: Green top (Lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 3 mL

Collection Instructions:  

  1. Centrifuge and separate cells after clot formation and within 4 hours of collection. 
  2. Keep tightly capped to prevent evaporation of CO2.

Specimen Minimum Volume

0.10 mL

Specimen Stability

Room temperature: 24 hours

Refrigerated: 7 days

Frozen: 2 weeks

Reference Range

22 - 29 mEg/L

Rejection Due To

Unlabeled, mislabeled, wrong tube type, QNS, severely hemolyzed samples 

Report Available

Same day

Clinical Significance

Carbon dioxide and phosphoenyl pyruvate (PEP) are converted to oxalacetate and phosphate catalyzed by PEP carboxylase. Oxalacetate is then reduced to malate while NADH is oxidized. The resulting decrease in absorbance is measured at 404nm and is proportional to the CO2 content in the sample.

Method Name

PEP Carboxylase



Day(s) Performed