Carbon Dioxide (Total) in Blood Gas Analysis
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).
["Your blood’s carbon dioxide levels help doctors check for respiratory or metabolic issues."]
Key facts at a glance
- LOINC
- 19888-7
- Short code
- CO2 VFr ExG IR Abs
- Synonyms
- CO2 VFr ExG IR Abs
- 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
- infrared-absorption
- 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?
Total carbon dioxide (CO₂) in your blood includes both dissolved CO₂ and bicarbonate ions (HCO₃⁻), which are key components of your body’s natural buffering system. This test reflects how efficiently your lungs remove CO₂ and how your kidneys adjust bicarbonate levels to maintain pH balance.
Why Might You Need This Test?
Doctors order this test to evaluate conditions like chronic obstructive pulmonary disease (COPD), respiratory failure, kidney disease, or metabolic disorders. It’s also used during surgeries, in intensive care, or when monitoring conditions that affect breathing or acid-base balance.
How Is This Test Done?
A small blood sample is taken from an artery (often in the wrist) and analyzed immediately in a blood gas machine. The test measures CO₂ pressure (PCO₂) and bicarbonate levels to determine your blood’s acidity and gas exchange status.
What Are Common Causes of Abnormal Results?
High CO₂ levels may indicate respiratory issues (e.g., hyperventilation, lung disease), while low levels could suggest rapid breathing, kidney problems, or metabolic acidosis. Extreme deviations may signal urgent medical attention.
Reference range
Adult: 22-28 mmol/LN/A
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.
This test is critical for diagnosing and managing conditions that disrupt normal acid-base homeostasis, such as respiratory acidosis (e.g., from COPD), metabolic alkalosis (e.g., from vomiting), or acute kidney failure. It helps guide treatments like oxygen therapy, breathing support, or fluid/electrolyte adjustments.
Short name
Total CO₂
Frequently asked questions
Could this test be affected by recent exercise or diet?
What if my results are outside the normal range?
Is this test painful?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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