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Total Carbon Dioxide in Blood (Plasma/Serum)

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

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

Quick summary

["Your blood’s CO₂ levels help determine if your body is producing too much or too little acid, which can affect breathing and overall health."]

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

Key facts at a glance

LOINC
2027-1
Short code
CO2 BldV-sCnc
Synonyms
CO2 BldV-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

What Does This Test Measure?

Total CO₂ in blood includes dissolved carbon dioxide (bicarbonate and carbonic acid) and reflects how efficiently your lungs remove CO₂ during breathing. It’s part of the acid-base balance system, which also involves oxygen and pH levels.

Why Might You Need This Test?

Doctors may order this test to check for conditions like respiratory issues (e.g., chronic obstructive pulmonary disease), metabolic disorders, or kidney problems that affect acid-base balance.

How Is the Test Done?

A small blood sample is taken from your arm, usually via a vein. The blood is sent to a lab where it’s analyzed to measure total CO₂ content.

What Are Common Causes of Abnormal Results?

High CO₂ levels (hypercapnia) may occur with poor lung function or overproduction of carbon dioxide. Low levels (hypocapnia) can happen with rapid breathing, kidney issues, or overuse of diuretics.

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 (Venous or Arterial Blood)

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within 1–2 business days, depending on your lab’s processing time. Your healthcare provider will discuss them with you during your follow-up visit.
Can I eat or drink anything before this test?
No special preparation is needed for this test. However, if you’re having an arterial blood draw (for arterial CO₂), you may need to fast or avoid caffeine for 30 minutes before.
Is this test painful?
The blood draw is usually mild discomfort for a few seconds, similar to a standard venipuncture. Most people tolerate it well. If you have a hard-to-reach vein, you may feel a slight pinch.
  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