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Carbon Dioxide in Blood (Total, Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of carbon dioxide dissolved in your blood plasma, which helps assess how well your body is balancing acidity and alkalinity (acid-base balance).

Quick summary

["This test helps evaluate your blood’s acid-base status and kidney function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
19223-7
Short code
CO2 BldMV-sCnc
Synonyms
CO2 BldMV-sCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
22
Ref high
28
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82374
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions affecting acid-base balance, such as respiratory or metabolic disorders. It’s also useful in diagnosing kidney issues or monitoring chronic conditions like kidney disease or heart failure.

What Does the Test Measure?

Total CO₂ in plasma reflects the amount of carbon dioxide carried in your blood, which is influenced by breathing patterns, kidney function, and metabolic processes. It indirectly measures bicarbonate levels, which are critical for maintaining blood pH.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The plasma portion is separated and analyzed to determine the CO₂ concentration using a specialized blood gas analyzer.

What Do Results Mean?

Results help identify whether your blood is too acidic (acidosis) or too alkaline (alkalosis). Abnormal levels may signal conditions like respiratory failure, kidney problems, or dehydration.

Reference range

Adult: 22-28 mmol/LN/A

Specimen: whole-blood

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Total CO₂ (Plasma)

Frequently asked questions

What causes abnormal CO₂ levels?
Abnormal CO₂ levels can result from conditions like chronic obstructive pulmonary disease (COPD), kidney disease, severe dehydration, or certain medications that affect breathing or metabolism.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition, symptoms, or treatment plan. Regular monitoring may be necessary for chronic illnesses like kidney disease or heart failure.
Can diet or lifestyle affect this test?
Dietary changes or lifestyle factors like exercise or hydration status may indirectly influence CO₂ levels, but they don’t directly affect this specific test. Your healthcare provider will consider these factors when interpreting results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy