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Endogenous Carbon Dioxide (Endogenous CO₂) in Blood Gas Analysis

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

This test measures the amount of carbon dioxide produced naturally by your body and dissolved in your blood. It helps assess how well your lungs are removing carbon dioxide and maintaining your blood chemistry balance.

Quick summary

["Your blood’s carbon dioxide levels are crucial for breathing health and acid-base balance."]

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

Key facts at a glance

LOINC
111863-7
Short code
Type of air-gas Endscpy
Synonyms
Type of air-gas Endscpy
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
endoscopy
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?

Endogenous carbon dioxide (CO₂) is generated continuously through metabolic processes, such as cellular respiration. Your body converts oxygen and nutrients into energy, releasing CO₂ as a byproduct. This test measures the concentration of CO₂ dissolved in your blood plasma, reflecting your body’s metabolic activity and respiratory function.

Why Is This Test Done?

Doctors may order this test as part of a blood gas analysis to evaluate lung function, diagnose conditions like respiratory failure, or monitor patients with chronic respiratory diseases (e.g., COPD). It also helps assess metabolic acidosis or alkalosis.

How Is the Test Performed?

A blood sample is taken from a vein (usually in your arm) and analyzed immediately in a lab using specialized equipment. The test measures the partial pressure of CO₂ in your blood, often alongside oxygen and pH levels.

What Are Common Causes of Abnormal Results?

Elevated levels may indicate hyperventilation, metabolic alkalosis, or certain lung disorders. Low levels can suggest hypoventilation, respiratory acidosis, or conditions like asthma or pneumonia.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Endogenous CO₂ levels are critical for diagnosing and managing respiratory and metabolic disorders. High or low values can signal imbalances that require immediate medical attention, such as breathing difficulties, fluid imbalances, or underlying lung diseases. It also guides treatment decisions, like adjusting oxygen therapy or managing acid-base disorders.

Short name

Endogenous CO₂

Frequently asked questions

What does a high endogenous CO₂ level mean?
A high endogenous CO₂ level may suggest your body is retaining too much CO₂, which can occur with conditions like chronic obstructive pulmonary disease (COPD), severe asthma, or certain metabolic issues. It may also indicate hypoventilation, where your lungs aren’t working as well as they should.
What does a low endogenous CO₂ level mean?
A low endogenous CO₂ level often means your body is removing CO₂ too quickly, which can happen with hyperventilation (breathing too fast) or conditions like anxiety attacks. It may also reflect metabolic alkalosis or overuse of certain medications that affect breathing.
How often should I get this test?
The frequency depends on your health condition. If you have chronic lung disease, respiratory issues, or are on oxygen therapy, your doctor may recommend regular monitoring. Otherwise, this test is usually done only when symptoms or medical concerns suggest it’s needed.
  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