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Arterial Blood Gas (ABG) with Calculated Carbon Dioxide Content (pCO₂) from Serum/Plasma

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

This test measures how much carbon dioxide is dissolved in your blood and helps assess your breathing and acid-base balance.

Quick summary

["Your blood’s carbon dioxide levels and breathing health are evaluated together with oxygen levels and pH balance."]

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

Key facts at a glance

LOINC
57922-7
Short code
CO2 SerPl Calc-sCnc
Synonyms
CO2 SerPl Calc-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
28
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
calculated
CPT
82374
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Does This Test Measure?

The test evaluates the concentration of carbon dioxide (CO₂) in your blood, typically measured as partial pressure (pCO₂). It also includes calculations for overall acid-base status, such as pH and bicarbonate levels, which help determine if your body is maintaining proper balance between acids and bases.

Why Might You Need This Test?

This test is often used to diagnose or monitor conditions affecting your lungs, such as chronic obstructive pulmonary disease (COPD), asthma, or other respiratory issues. It can also help identify problems with how your kidneys balance acids and bases, or assess severe illness like heart failure or sepsis.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum or plasma, which is then analyzed to determine CO₂ levels and related measurements. This test is typically performed on fresh or refrigerated samples.

Common Conditions Monitored

ABG with pCO₂ is critical in diagnosing respiratory disorders, metabolic imbalances, and severe medical emergencies. It helps doctors determine if you need oxygen therapy, adjust medications, or plan further treatment based on your blood chemistry.

Reference range

Adult: 22-28 mmol/LN/A

Specimen: serum

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

ABG with pCO₂

Frequently asked questions

How is this test different from a regular blood test?
Unlike standard blood tests that measure individual substances like glucose or cholesterol, this test specifically evaluates the gases (oxygen and carbon dioxide) dissolved in your blood and calculates acid-base balance metrics. It requires special equipment and immediate analysis to get accurate results.
What does a normal pCO₂ level mean?
A normal pCO₂ level is not a single number but part of a balanced system. While exact ranges can vary by lab, a typical pCO₂ value is around 35–45 mmHg, but this depends on your overall health and the context of your test. Your doctor will interpret the results in relation to your symptoms and other test results.
Can I eat or drink before this test?
For most ABG tests, you may need to fast for a few hours before the procedure, depending on your doctor’s instructions. However, if you’re having this test for immediate clinical reasons (like severe illness), you may not be able to follow fasting guidelines. Always follow your healthcare provider’s specific instructions.
  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